Proceedings of the 2014 National Toxicology Program Satellite Symposium

Abstract

The 2014 annual National Toxicology Program (NTP) Satellite Symposium, entitled "Pathology Potpourri" was held in Washington, D.C., in advance of the Society of Toxicologic Pathology's 33rd annual meeting. The goal of this annual NTP Symposium is to present current diagnostic pathology or nomenclature issues to the toxicologic pathology community. This article presents summaries of the speakers' presentations, including diagnostic or nomenclature issues that were presented, along with select images that were used for audience voting and discussion. Some lesions and topics covered during the symposium included a pulmonary mucinous adenocarcinoma in a male B6C3F1 mouse; plexiform vasculopathy in Wistar Han (Crl:WI[Han]) rats; staging of the estrous cycle in rats and mice; peri-islet fibrosis, hemorrhage, lobular atrophy and inflammation in male Sprague-Dawley (SD) rats; retinal dysplasia in Crl:WI[Han] rats and B6C3F1 mice; multicentric lymphoma with intravascular microemboli and tumor lysis syndrome, and 2 cases of myopathy and vascular anomaly in Tg.rasH2 mice; benign thymomas in Crl:WI[Han] rats; angiomatous lesions in the mesenteric lymph nodes of Crl:WI[Han] rats; an unusual foveal lesion in a cynomolgous monkey; and finally a series of nomenclatures challenges from the endocrine International Harmonization of Nomenclature and Diagnostic Criteria (INHAND) Organ Working Group (OWG).

Keywords: NTP Satellite Symposium; acute tumor lysis syndrome.; chronic-active pancreatitis; endocrine nomenclature; fovea cyst; mesenteric lymph node angiomatous lesion; mucinous adenoma; plexiform vasculopathy; retinal dysplasia; thymoma; vaginal cytology.

Figure 1

Mucinous adenoma in the lung of an untreated control male B6C3F1 mouse. Low power view of lung mass (A, arrow). Note adjacent bronchus (Br). Bv = Blood vessel (H&E). Higher magnification of lung mass (B). Lung mass consists primarily of acinar-like structures (a) lined by non-ciliated, columnar epithelial cells with abundant, pale bluish-pink cytoplasm and generally small, uniform, basal nuclei arranged in single rows. Supporting fibrous stroma (f) exhibits a mixed inflammatory cell infiltrate (H&E). Figure C shows acinar cells that exhibit strongly positive cytoplasmic staining with periodic acid Schiff (PAS) reaction with diastase (left) (magenta) and Alcian blue at pH 2.5 (right) (turquoise). Most cells lining acinar structures (a) in Figure D are negative for CCSP (club [Clara] cell-specific protein). Only a few scattered single cells exhibit CCSP-positivity (short arrow). Note rare mitotic figure (long arrow). Cells lining acinar structures (a) in Figure E are negative for SPC (surfactant protein C). Mucinous cells in Figure F extend along existing alveolar septa (lepidic growth) (arrows) at border of mass (M) (H&E). Alveolar parenchyma (AP). b = bronchioles entrapped at periphery of mass.

Figure 2

Plexiform vasculopathy in Wistar Han rats. Low (A) and high (B) magnification photomicrographs from a large mediastinal vessel. Note the formation of numerous variably-sized and shaped endothelial-lined vascular spaces expanding the tunica media of the vessel. Figures C and D are low and high magnification photomigrographs (respectively), of a mesenteric vessel, likely a vein, with numerous tortuous, incomplete endothelial-lined vascular spaces expanding/dissecting through the tunica media. Little inflammation was associated with these vascular lesions, and the endothelial cells lining the spaces in panels are relatively flattened and quiescent with no evidence of pleomorphism or mitotic figures. H&E Vascular changes seen more commonly within the current study are illustrated in Figures E–G from the kidney and Figure H from the mediastinum. Lesions include medial changes such as vacuolation (E, arrows), cytoplasmic necrosis and hemorrhage (E and H, white arrowheads), subintimal deposition of serum proteins which is often referred to as “fibrinoid necrosis” (F and G, arrows) and varying severity of adventitial inflammation (Figures E–H, black arrowheads). H&E

Figure 2

Plexiform vasculopathy in Wistar Han rats. Low (A) and high (B) magnification photomicrographs from a large mediastinal vessel. Note the formation of numerous variably-sized and shaped endothelial-lined vascular spaces expanding the tunica media of the vessel. Figures C and D are low and high magnification photomigrographs (respectively), of a mesenteric vessel, likely a vein, with numerous tortuous, incomplete endothelial-lined vascular spaces expanding/dissecting through the tunica media. Little inflammation was associated with these vascular lesions, and the endothelial cells lining the spaces in panels are relatively flattened and quiescent with no evidence of pleomorphism or mitotic figures. H&E Vascular changes seen more commonly within the current study are illustrated in Figures E–G from the kidney and Figure H from the mediastinum. Lesions include medial changes such as vacuolation (E, arrows), cytoplasmic necrosis and hemorrhage (E and H, white arrowheads), subintimal deposition of serum proteins which is often referred to as “fibrinoid necrosis” (F and G, arrows) and varying severity of adventitial inflammation (Figures E–H, black arrowheads). H&E

Figure 3

Rodent vaginal cytology (A) Many neutrophils (arrows), characterized by their very small size and multilobulated nuclei, and two large nucleated epithelial cells (arrowhead) are present on this diestrous vaginal smear from a Sprague Dawley rat (Toluidine blue stain). (B) Small nucleated epithelial cells from a proestrous vaginal smear of a Sprague Dawley rat. Lower numbers of anucleated epithelial cells are also seen (right center) (Toluidine blue stain). (C) Several large nucleated epithelial cells (arrows) are intermixed with anucleated epithelial cells (arrowheads) from a Sprague Dawley rat vaginal smear of late estrus. Bacteria are adhered to many of the epithelial cells (Modified Wright–Giemsa stain). (D) Anucleated epithelial cells from a vaginal smear of estrus in a B6C3F1/N mouse. Some cells possess ghost nuclei (arrows) (Modified Wright – Giemsa stain). (E) Vaginal smear of proestrus in a Sprague Dawley rat characterized by high numbers of small nucleated epithelial cells found individually and in cohesive clusters (arrow) (Toluidine blue stain). (F) Vaginal smear of estrus in a Sprague Dawley rat characterized by high numbers of anucleated epithelial cells (Modified Wright – Giemsa stain). (G) Vaginal smear of late estrus in a Sprague Dawley rat characterized by the presence of round, oval and spindle shaped nucleated epithelial cells interspersed among anucleated epithelial cells (Modified Wright – Giemsa stain). (H) Vaginal smear of metestrus in a B6C3F1/N mouse. Neutrophils are seen among anucleated epithelial cells (Modified Wright – Giemsa stain). (I) Vaginal smear of metestrus in a Sprague Dawley rat. Neutrophils, small and large nucleated epithelial cells and anucleated cells are all present (Toluidine blue stain). (J) Vaginal smear of metestrus in a B6C3F1/N mouse. At the peak of metestrus, a flood of neutrophils is seen among the anucleated epithelial cells resulting in smears of high cellularity (Toluidine blue stain). (K) Vaginal smear of diestrus in a Sprague Dawley rat. Neutrophils are widely scattered among low numbers of epithelial cells (Modified Wright–Giemsa stain). (L) A low cellularity diestrous vaginal smear in a B6C3F1/N mouse consisting of scattered neutrophils and epithelial cells. Modified Wright – Giemsa stain.

Figure 3

Rodent vaginal cytology (A) Many neutrophils (arrows), characterized by their very small size and multilobulated nuclei, and two large nucleated epithelial cells (arrowhead) are present on this diestrous vaginal smear from a Sprague Dawley rat (Toluidine blue stain). (B) Small nucleated epithelial cells from a proestrous vaginal smear of a Sprague Dawley rat. Lower numbers of anucleated epithelial cells are also seen (right center) (Toluidine blue stain). (C) Several large nucleated epithelial cells (arrows) are intermixed with anucleated epithelial cells (arrowheads) from a Sprague Dawley rat vaginal smear of late estrus. Bacteria are adhered to many of the epithelial cells (Modified Wright–Giemsa stain). (D) Anucleated epithelial cells from a vaginal smear of estrus in a B6C3F1/N mouse. Some cells possess ghost nuclei (arrows) (Modified Wright – Giemsa stain). (E) Vaginal smear of proestrus in a Sprague Dawley rat characterized by high numbers of small nucleated epithelial cells found individually and in cohesive clusters (arrow) (Toluidine blue stain). (F) Vaginal smear of estrus in a Sprague Dawley rat characterized by high numbers of anucleated epithelial cells (Modified Wright – Giemsa stain). (G) Vaginal smear of late estrus in a Sprague Dawley rat characterized by the presence of round, oval and spindle shaped nucleated epithelial cells interspersed among anucleated epithelial cells (Modified Wright – Giemsa stain). (H) Vaginal smear of metestrus in a B6C3F1/N mouse. Neutrophils are seen among anucleated epithelial cells (Modified Wright – Giemsa stain). (I) Vaginal smear of metestrus in a Sprague Dawley rat. Neutrophils, small and large nucleated epithelial cells and anucleated cells are all present (Toluidine blue stain). (J) Vaginal smear of metestrus in a B6C3F1/N mouse. At the peak of metestrus, a flood of neutrophils is seen among the anucleated epithelial cells resulting in smears of high cellularity (Toluidine blue stain). (K) Vaginal smear of diestrus in a Sprague Dawley rat. Neutrophils are widely scattered among low numbers of epithelial cells (Modified Wright–Giemsa stain). (L) A low cellularity diestrous vaginal smear in a B6C3F1/N mouse consisting of scattered neutrophils and epithelial cells. Modified Wright – Giemsa stain.

Figure 4

Pancreatic lesions from a male Sprague Dawley rat. (A and B) Pancreas sections at low and higher magnifications from a male Sprague Dawley rat treated with test-article. Note the locally extensive, perilobular to lobular inflammation and fibroplasia. (C) Atrophic pancreatic acini from the same section with mononuclear to mixed inflammation and fibroplasia. (D) Affected pancreatic islet from the same section with hemorrhage, hemosiderin containing macrophages, inflammation and fibroplasia. H&E

Figure 5

Retinal dysplasia in Wistar Han rats and B6C3F1 mice. (A) Wistar Han rat eye with disorganized, circular folding of retinal layers consistent with retinal dysplasia. (B) B6C3F1 mouse eye with similar histologic features as that seen in Figure A. (C) Coronal section of developing eye from a mouse embryo day 17.5. Note immature appearance of the retinal layers. H&E

Figure 6

(A–E) Acute tumor lysis syndrome (ATLS) in a male Tg.ras H2 mouse with disseminated lymphoma. There are multifocal intravascular clumps (emboli) of basophilic material (arrow) in lungs, adrenal glands, kidneys, liver and heart. These emboli are either admixed with fibrillary eosinophilic material in lungs (A) or observed as elongated homogenous, acellular and basophilic microemboli in small vessels of glomeruli, adrenal cortex, liver and heart (B–E). (F–H) Skeletal muscle (thigh) of female Tg.rasH2 mouse with skeletal myopathy. At low magnification (F), there are multifocal to coalescing areas of muscle degeneration admixed with inflammatory infiltrate. Inflammatory cells include neutrophils, lymphocytes, and macrophages (G). The regenerating fibers showed basophilic cytoplasm and nuclear rowing (H) (H&E).

Figure 7

Benign thymomas in Wistar Han rats. Case 1, an affected thymus from a female rat was subgrossly characterized by a roundish, unencapsulated mass with smooth margins that had totally effaced the normal thymus architecture (A). At higher magnification (B) the mass was predominantly composed of small lymphocytes with dark basophilic, densely condensed nuclei and little cytoplasm that somewhat masked an underlying population of larger epithelial cells (B, arrows), with large vesicular nuclei and moderate to abundant pale eosinophilic cytoplasm. Cytokeratin-18 immunohistochemically stained slides of a control thymus (C), and the same thymus depicted in Figures A and B (D), illustrates the increased epithelial cell population, which has brown cytoplasmic staining within the tumor as compared to the control. Case 2, an affected thymus from a female rat contains a roundish, mostly encapsulated, expansile mass (E, arrowheads) with a cytologic pattern differing from that of the adjacent unaffected thymus, including multiple small pale staining cellular clusters (E, arrows). Cytokeratin-18 immunohistochemically stained slides (F) of the tumor from 7E reveal increased numbers of cytokeratin-18 immunopositive cells within the tumor (demarcated by arrowheads), and better highlights the fibrous capsule surrounding the tumor. Low- (G) and high- (H) magnification images are from larger thymomas from female rats with a medullary differentiation pattern, which consists of abundant lymphocytes, often found cuffing variably-sized clusters of pale-staining cells (G, arrowheads; H, higher magnification). Low magnification image (I) from a malignant thymoma from a male rat, depicting a predominant ovoid neoplastic epithelial cell population effacing the thymus (arrows). Some extent of squamous differentiation is visible at higher magnification in this malignant thymoma (J). A benign, predominantly epithelial, thymoma from a male rat with both ovoid and spindle shaped neoplastic cells (K). Occasionally thymomas can have multiple cytologic patterns (L), though it is possible that this lesion from a female rat may represent three distinct tumors expanding separate lobules of the thymus, with a small amount of residual, atrophied thymus at the bottom of the figure (arrows).

Figure 7

Benign thymomas in Wistar Han rats. Case 1, an affected thymus from a female rat was subgrossly characterized by a roundish, unencapsulated mass with smooth margins that had totally effaced the normal thymus architecture (A). At higher magnification (B) the mass was predominantly composed of small lymphocytes with dark basophilic, densely condensed nuclei and little cytoplasm that somewhat masked an underlying population of larger epithelial cells (B, arrows), with large vesicular nuclei and moderate to abundant pale eosinophilic cytoplasm. Cytokeratin-18 immunohistochemically stained slides of a control thymus (C), and the same thymus depicted in Figures A and B (D), illustrates the increased epithelial cell population, which has brown cytoplasmic staining within the tumor as compared to the control. Case 2, an affected thymus from a female rat contains a roundish, mostly encapsulated, expansile mass (E, arrowheads) with a cytologic pattern differing from that of the adjacent unaffected thymus, including multiple small pale staining cellular clusters (E, arrows). Cytokeratin-18 immunohistochemically stained slides (F) of the tumor from 7E reveal increased numbers of cytokeratin-18 immunopositive cells within the tumor (demarcated by arrowheads), and better highlights the fibrous capsule surrounding the tumor. Low- (G) and high- (H) magnification images are from larger thymomas from female rats with a medullary differentiation pattern, which consists of abundant lymphocytes, often found cuffing variably-sized clusters of pale-staining cells (G, arrowheads; H, higher magnification). Low magnification image (I) from a malignant thymoma from a male rat, depicting a predominant ovoid neoplastic epithelial cell population effacing the thymus (arrows). Some extent of squamous differentiation is visible at higher magnification in this malignant thymoma (J). A benign, predominantly epithelial, thymoma from a male rat with both ovoid and spindle shaped neoplastic cells (K). Occasionally thymomas can have multiple cytologic patterns (L), though it is possible that this lesion from a female rat may represent three distinct tumors expanding separate lobules of the thymus, with a small amount of residual, atrophied thymus at the bottom of the figure (arrows).

Figure 8

Angiomatous lesions in the mesenteric lymph nodes of male Wistar Han rats from a 2-year toxicity/carcinogenicity bioassay. Figure A is a high magnification of a hemangiosarcoma from case 1. Neoplastic cells are arranged in variably sized vascular spaces that are small, round to anastomosing, and supported by a fibrovascular stroma. Figure B is a high magnification of a hemagioma from Case 2. This lesion is characterized by a proliferation of variably sized cavernous spaces lined by a single layer of well-differentiated neoplastic cells. Cases 3 and 4 are examples of angiomatous hyperplasia. Figure C shows the lesion from case 3 as a well-demarcated focal lesion, whereas Figure D shows the lesion from case 4 as a larger, more infiltrative lesion. Figures E and F show the similar tissue architecture and cellular morphology of cases 3 and 4, respectively. Both are characterized by a focally extensive non-neoplastic change composed of increased number of proliferating endothelial cells and blood filled vessels and spaces supported by varying quantities of fibrovascular stroma. The endothelial cells lack cellular atypia.

Figure 9

Retinal foveal lesion in a cynomolgus monkey. Figure A is a normal fovea centralis (fovea) from a control animal. There is a slight depression in this area of the retina. Although not apparent by light microscopy, the central foveola region is avascular, contains only cone photoreceptors and Müller cells. Figure B is a low magnification image from one ocular globe of the affected animal. The optic nerve is within normal limits but there is hypertrophy and vacuolization of the various layers of the fovea. The sclera, choroid, and pigmented epithelial layer are all within normal limits. Figures C and D are higher magnifications, showing the hypertrophy and vacuolization in the inner and outer plexiform and photoreceptor layers of the fovea centralis.

Figure 10

Figures A–C illustrate focal lesions in the rat adrenal cortex. (A) Focal lesion with reduced cytoplasmic vacuolation and equivocal increased number of cortical cells. Consensus was not reached for this lesion. Preferred diagnoses were vacuolation, decreased, focal or hyperplasia, focal. (B) Hyperplasia, focal, large cell type with nuclear atypia. Many pathologists preferred hypertrophy, focal as the best diagnosis for this lesion. Adrenal capsule is on the left. (C) Vacuolation, increased, focal. There was a high degree of concurrence on this lesion. Figures D (H&E stain) and E (BrdU stain) illustrate hyperplasia, focal, large cell type, adrenal cortex, rat. Note the increased cell proliferation towards the outer or subcapsular region of the nodule with reduced cell proliferation towards the inner region of the nodule. Figure F illustrates thyroid dysplasia in a Wistar Hannover GALAS rat. Note the enlarged follicular cells (hypertrophy) with large basilar cytoplasmic vacuoles containing eosinophilic proteinaceous fluid and apical displacement of the nucleus. Images A–C are courtesy of Dr. M. Hoenerhoff and the NTP Archives. Images D and E are courtesy of BASF SE. Figures 10G and 10H illustrate aberrant craniopharyngeal structures in a rat pituitary gland. (G) Aberrant glandular structures are present between the pars intermedia and pars nervosa (arrow) with infiltration into the pars nervosa. Note the Rathke’s cleft cyst (arrowhead). (H). Aberrant glandular structures in the pars nervosa with similarity to the parotid salivary gland. A Rathke’s cleft cyst is present on the left.

Figure 10

Figures A–C illustrate focal lesions in the rat adrenal cortex. (A) Focal lesion with reduced cytoplasmic vacuolation and equivocal increased number of cortical cells. Consensus was not reached for this lesion. Preferred diagnoses were vacuolation, decreased, focal or hyperplasia, focal. (B) Hyperplasia, focal, large cell type with nuclear atypia. Many pathologists preferred hypertrophy, focal as the best diagnosis for this lesion. Adrenal capsule is on the left. (C) Vacuolation, increased, focal. There was a high degree of concurrence on this lesion. Figures D (H&E stain) and E (BrdU stain) illustrate hyperplasia, focal, large cell type, adrenal cortex, rat. Note the increased cell proliferation towards the outer or subcapsular region of the nodule with reduced cell proliferation towards the inner region of the nodule. Figure F illustrates thyroid dysplasia in a Wistar Hannover GALAS rat. Note the enlarged follicular cells (hypertrophy) with large basilar cytoplasmic vacuoles containing eosinophilic proteinaceous fluid and apical displacement of the nucleus. Images A–C are courtesy of Dr. M. Hoenerhoff and the NTP Archives. Images D and E are courtesy of BASF SE. Figures 10G and 10H illustrate aberrant craniopharyngeal structures in a rat pituitary gland. (G) Aberrant glandular structures are present between the pars intermedia and pars nervosa (arrow) with infiltration into the pars nervosa. Note the Rathke’s cleft cyst (arrowhead). (H). Aberrant glandular structures in the pars nervosa with similarity to the parotid salivary gland. A Rathke’s cleft cyst is present on the left.