Adenocarcinoma cells in effusion cytology as a diagnostic pitfall with potential impact on clinical management: a case report with brief review of immunomarkers

Abstract

Distinguishing metastatic carcinoma cells from reactive mesothelial cells in effusion samples is often challenging based on morphology alone. Metastatic carcinoma cells in fluid samples may mimic reactive mesothelial cells due to overlapping cytological features. We report a case of a pleural effusion in a 51-year-old female patient with a medical history significant for bilateral ovarian tumors and peritoneal implants diagnosed as serous tumor of borderline malignant potential. The effusion was composed almost entirely of adenocarcinoma cells that morphologically mimicked reactive mesothelial cells. The diagnosis of metastatic adenocarcinoma was made after a wide immunostaining panel of antibodies. Recognizing metastatic adenocarcinoma cells in effusion samples can be challenging and an accurate diagnosis may have significant impact on clinical management as demonstrated by this case.

Keywords: adenocarcinoma cells; cytology; effusion; immunostaining; reactive mesothelial cells.

Figure 1.

A: Hematoxylin and eosin (H&E) stained cell-block section showing atypical cells with predominantly round nuclei, occasional binucleation (arrowhead), prominent nucleoli, and abundant, often dense cytoplasm, some containing cytoplasmic vacuoles, singly and in small groups, some showing “scalloped borders” (arrow). B: In some areas the atypical cells had “windows” between them (arrowhead) and some groups showed acinar-like structures (arrow). C: Histology section of the surgical pathology material from the patient’s ovarian tumor showing a serous tumor with enlarged hyperchromatic nuclei.

Figure 1.

A: Hematoxylin and eosin (H&E) stained cell-block section showing atypical cells with predominantly round nuclei, occasional binucleation (arrowhead), prominent nucleoli, and abundant, often dense cytoplasm, some containing cytoplasmic vacuoles, singly and in small groups, some showing “scalloped borders” (arrow). B: In some areas the atypical cells had “windows” between them (arrowhead) and some groups showed acinar-like structures (arrow). C: Histology section of the surgical pathology material from the patient’s ovarian tumor showing a serous tumor with enlarged hyperchromatic nuclei.

Figure 1.

A: Hematoxylin and eosin (H&E) stained cell-block section showing atypical cells with predominantly round nuclei, occasional binucleation (arrowhead), prominent nucleoli, and abundant, often dense cytoplasm, some containing cytoplasmic vacuoles, singly and in small groups, some showing “scalloped borders” (arrow). B: In some areas the atypical cells had “windows” between them (arrowhead) and some groups showed acinar-like structures (arrow). C: Histology section of the surgical pathology material from the patient’s ovarian tumor showing a serous tumor with enlarged hyperchromatic nuclei.

Figure 2.

Immunohistochemical staining on cell block sections show that the atypical cells stain positive for A: CA19.9, B: Claudin 4, and C: focally positive for B72.3. D: Calretinin stains background mesothelial cells and is negative in the large atypical cells.