Spindle Cell Sarcoma

Although the diagnosis was established based on morphology and immunoprofile, adverse histologic features, such as increased mitotic activity and high cellularity, suggest potential malignant behavior, warranting close clinical follow-up. This case underscores the importance of thorough histopathological and immunohistochemical evaluation in distinguishing SFT from other spindle cell lesions of the prostate, particularly given its extreme rarity and potential implications for patient management and follow-up.

Epstein-Barr virus (EBV)-associated smooth muscle rare tumors (EBV-SMTs) in HIV patients with low CD4 counts require clinical suspicion and Epstein-Barr virus (EBV) involvement in brain tumor diagnosis. Early HIV detection, CD4 monitoring, and antiretroviral therapy (ART) management can decrease the risk of these malignancies.

Notably, positive cyclin D1 expression in metastatic malignant PT could be a diagnostic challenge, if not carefully considered within clinical context. Furthermore, the significant difference in cyclin D1 expression between malignant PT and triple-negative metaplastic spindle cell carcinoma highlights its potential utility in distinguishing between them.

The patient underwent a right mastectomy, achieving a surgical clearance. After 3 months, he passed away with malignant pleural effusion due to lung metastasis.

It also underscores the critical role of immunohistochemistry, particularly STAT6 staining, in distinguishing SFT from histologic mimics. Vigilant follow-up remains essential, especially in atypical or CD34-negative cases, given their potential for aggressive behavior.

This case highlights the critical role of molecular testing in the diagnosis of LGFMS and emphasizes the importance of appropriate management strategies, including aggressive local control and long-term surveillance, given the tumor's risk of late recurrence and distant metastasis.

However, adjuvant chemotherapy significantly led to better overall survival. The Hippo pathway is frequently deregulated (nuclear YAP/TAZ in 61.4% of patients), suggesting it is a compelling novel therapeutic target for this aggressive disease.

By sharing the diagnosis and treatment process of this patient and reviewing the relevant literature, we aim to help clinicians enhance their understanding of two rare diseases, namely pleomorphic RMS and sarcomatoid carcinoma of the liver.

While many morphologic features of vascular lesions at this site are shared with those of extra-genital soft tissues, pathologists must be aware that these tumours may occur in the vulvovaginal area and display unconventional clinical profiles. As such, a broad differential for epithelioid and spindle cell neoplasms at this site is prudent.

Concurrent comprehensive genome profiling (FoundationOne® CDx) confirmed the LMNA-NTRK1 fusion, and treatment with the TRK inhibitor larotrectinib was started. With larotrectinib treatment, the tumor shrank in size at an early stage, and the response has been maintained for > 2 years.

This study suggests that pan-TRK immunostaining may be useful for confirming neural differentiation in MPNST. However, whether its positivity reflects NTRK rearrangements or neural differentiation must be carefully assessed in combination with various immunohistochemical and molecular tests.

This case demonstrates the critical role of immunohistochemistry in confirming synchronous primary tumors. For complex, locally advanced disease, radical upfront en bloc resection remains the gold standard for achieving curative-intent, negative margins, even in the elderly.