ABSTRACT
Pseudoangiomatous spindle cell lipoma is a rare pattern within the spindle cell lipoma spectrum that exhibits a remarkable histological pattern characterized by its resemblance to vascular lesions, creating a pseudoangiomatous appearance. Approximately 20 to 30 reports have been described in the literature. In this context, we present an intriguing report of pseudoangiomatous spindle cell lipoma showcasing a unique low-fat pseudo angiomatous pattern in a 61-year-old male patient presented with a 6-cm subcutaneous mass on his right arm, which was thoroughly investigated and subsequently excised. Microscopic examination revealed bland spindle cells infiltrates within a fibromyxoid stroma. Notably, the tumor exhibited distinctive branching and dilated vascular-like spaces that formed pseudopapillary (villiform) projections. Interestingly, the tumor displayed certain regions featuring mature adipose tissue components, alongside hyalinized blood vessels. No necrosis, atypical spindle cells, increased mitotic activity, or pleomorphic lipoblasts were observed. The immunohistochemical evaluation demonstrated diffuse positive staining for CD34 and negative staining for STAT6. This report of a low-fat pattern of pseudoangiomatous spindle cell lipoma underscores the importance of recognizing and characterizing rare entity subtype for accurate diagnosis and appropriate management. This report contributes to the expanding understanding of the diverse presentations of pseudo angiomatous spindle cell lipomas and underscores the significance of comprehensive histopathological assessment.
ABSTRACT
BACKGROUND: Muir-Torre syndrome (MTS) is a rare genetic disorder that is caused by mismatch repair (MMR) protein mutations. MTS increases the risk of developing skin and gastrointestinal tumors such as sebaceous adenomas (SAs), sebaceous carcinomas, colorectal cancer, endometrial cancer, and ovarian cancer. The risk of developing these types of tumors varies depending on the involved mutation and the individual's family history risk. CASE PRESENTATION: A 47-year-old male presented with multiple skin lesions on the scalp, face, flank, and back. The examination revealed well-circumscribed, dome-shaped papules with a yellowish appearance with white oily material in the center. Histopathologic examination showed a well-circumscribed sebaceous neoplasm consistent with a mixture of basaloid cells and lobules of bland-appearing mature adipocytes that communicate directly to the surface epithelium. Focal cystic changes and peritumoral lymphocytic infiltrate were noted. Increased mitotic figures were seen in the basaloid cell component. The overall findings were consistent with the diagnosis of SAs. MMR staining showed preserved expression in MLH1 and PMS2 proteins, while MSH2 and MSH6 staining showed loss of protein expression. A screening colonoscopy showed numerous colon and rectal tumors, prompting concerns about the likelihood of MTS. Surgical intervention was pursued for complete resection. Histology revealed a diagnosis of mucinous adenocarcinoma/adenocarcinoma with mucinous features of the colon. The diagnosis of MTS was supported by molecular testing that revealed MSH2 germline mutation. The increased likelihood of MTS was attributed to the occurrence of SAs in unusual locations of the head and neck regions, unlike typical cases. CONCLUSION: MTS is a rare clinical condition that necessitates prompt thorough evaluation and periodic surveillance. When SA is encountered in atypical locations, it is important to consider additional testing supported by immunohistochemical staining, molecular testing, and regular screening to exclude the likelihood of MTS.
