An unusual case of primary splenic soft part alveolar sarcoma: case report and review of the literature with emphasis on the spectrum of TFE3-associated neoplasms

Abstract

Background: Alveolar soft part sarcoma is a rare tumour of soft tissues, mostly localized in muscles or deep soft tissues of the extremities. In rare occasions, this tumour develops in deep tissues of the abdomen or pelvis.

Case presentation: In this case report, we described the case of a 46 year old man who developed a primary splenic alveolar soft part sarcoma. The tumour displayed typical morphological alveolar aspect, as well as immunohistochemical profile notably TFE3 nuclear staining. Detection of ASPSCR1 Exon 7::TFE3 Exon 6 fusion transcript in molecular biology and TFE3 rearrangement in FISH confirmed the diagnosis.

Conclusion: We described the first case of primary splenic alveolar soft part sarcoma, which questions once again the cell of origin of this rare tumour.

Keywords: Alveolar soft part sarcoma; Splenic; TFE3.

Fig. 1

Imaging evaluation after 4 years of the initial symptomatology showing a 106 mm lobulated heterogenic and hypermetabolic splenic mass. A : Axial abdominal MRI. B : Frontal abdominal CT-scan. C : Whole body TEP-scan (SUVmax = 16.9). Arrows indicating splenic tumour mass with no other identified lesion

Fig. 2

Pathology analysis of the splenic specimen. A : Macroscopic appearance of the splenic lesion (after formaldehyde fixation). Note the proximity of the tumor with the large diameter vessels of the spleen. B : low magnification (x100) emphasizing pseudo-alveolar architecture. C : High magnification (x200) focally revealed marked nuclear atypia. D : High magnification (x630) showing intracytoplasmic diastase-resistant rod-like structures on the PAS coloration (black arrows). Bar scales indicate respectively 100, 40 and 4 μm

Fig. 3

Immunohistochemical and FISH analysis of the splenic tumour. A : Highly vascularized pattern between tumour nests highlighted by CD31 immunostaining. B : Nuclear diffuse TFE3 immunostaining of tumour cells. C-D : Heterogenous staining with Smooth muscle actin and Desmin antibodies. E : Illustration of TFE3 rearrangement in FISH. White arrows indicating break apart (split) signal in the majority of nuclei. F : PDL1 staining showing a weak to moderate but diffuse staining of tumour cells (TPS score > 90% and CPS score at 95). Bar scales indicate 100 μm for A, B and F, 40 μm for C-D