Primary alveolar soft part sarcoma of uterine corpus: a case report with immunohistochemical, ultrastructural study and review of literature

Abstract

Background: Alveolar soft part sarcoma (ASPS) is a rare mesenchymal malignancy. ASPS usually occurs most commonly in the deep soft tissues of the thigh and buttock or the head and neck regions. ASPS that originate from the uterine corpus are even more rare, with only 10 previous cases reported in the English literature.

Case presentation: In our case, the alveolar features were completely lost and the tumour shows a solid, non-alveolar pattern and the nuclei have marked variation in nuclear size, and multinucleation. The correct pathological diagnosis has been made by immuno- histochemical and ultrastructural features, which rvealed overexpression of TFE3 and peculiar cytoplasmic crystalline inclusions. In this paper, an additional case of primary ASPS of uterine corpus is reported with immunohistochemical, ultrastructural study and review of literature in the effort to delineate its clinical and pathological features. In this unusual site, the diagnosis can be problematic because ASPS can mimic other primary or metastatic uterine neoplasms.

Conclusions: Thus, in this unusual presentation an essential diagnostic marker is the nuclear over-expression of TFE3 as well as ultrastructural study, which reveals the presence of peculiar cytoplasmic crystalline inclusions.

Fig. 1

On cut sections, the tumour was well circumscribed, soft, with irregular border and showed areas which varied from yellow, brownish and grey, with a central haemorrhagic area

Fig. 2

Histologically, the tumour showed nests of neoplastic cells with abundant eosinophilic granular cytoplasm, distinct borders and vesicular nuclei with prominent nucleoli (a haematoxylin and eosin stain ×400). Extensive degenerative changes, such as hyalinization with haemorrhagic and hemosiderin deposits, were observed (b haematoxylin and eosin stain ×200). Other cells were large with clear vacuolated cytoplasms (c haematoxylin and eosin stain ×400). In some areas, the organoid pattern was lost and the tumour showed solid growth, made spindle cells with nuclear, pleomorphism, hyperchromasia, pseudo-inclusions and multinucleations (d haematoxylin and eosin stain ×200)

Fig. 3

Ki 67 index was very low (a ×200). Strong nuclear positivity to TFE3 was observed in all cells (b ×200)

Fig. 4

In an ultrastructural study, neoplastic cells had cytoplasmic crystalline inclusions (arrows) showing unidirectional periodicity