Expanding the Clinicopathologic and Molecular Spectrum of Lipoblastoma-Like Tumor in a Series of 28 Cases

Lipoblastoma-Like Tumor of the Tongue With IDH1 Mutation: A Case Report and Literature Review

BACKGROUND

Lipoblastoma-like tumors (LLTs) are uncommon lipogenic neoplasms that predominantly occur in the vulva of female individuals. This study presents a novel case of LLT located on the tongue with an IDH1 mutation. Both the site of occurrence and molecular alterations are reported for the first time.

CASE PRESENTATION

A 65-year-old female patient presented to the hospital 1 month ago with an incidental finding of a multinodular mass at the right lingual margin. We performed an incision along the outer edge of the mass and completely excised it 0.5 cm beyond its periphery. The final pathological diagnosis after routine examination confirmed a lipoblastoma-like tumor. Furthermore, Next-generation sequencing revealed the presence of mutations in IDH1.

CONCLUSIONS

This study presents the first documented case of LLT, thereby expanding its anatomical site of tongue and confirming the presence of a significant IDH1 mutation, thus enhancing our understanding of the molecular alterations in LLT.

Lipoblastoma-like tumor of the inguinal region: a close mimicker of myxoid liposarcoma

Lipoblastoma-like tumor is a rare mesenchymal neoplasm, typically arising in the vulvar region of young women. Although it is considered a benign tumor, rare local recurrences and exceptionally distant metastases have been reported. Histological examination reveals a well-circumscribed tumor with lobulated pattern, composed of a mixture of mature adipocytes, spindle cells and lipoblasts set in abundant myxoid stroma with numerous thin-walled capillary-like vessels. Due to the rarity of this neoplasm and its morphological resemblance with other benign and malignant lipomatous tumors, the diagnosis of lipoblastoma-like tumor is often challenging. Herein, we present a case occurring in the inguinal region of a 28-year-old woman. Histological examination showed a mixture of mature adipocytes, bland-looking spindle cells with fibrillary cytoplasm, and numerous univacuolated lipoblasts set in a prominent myxoid matrix containing numerous thin-walled branching vessels. Immunohistochemically, neoplastic cells showed diffuse immunostaining for CD34 and negativity for α-smooth muscle actin, desmin, Rb1, MDM2 and STAT6. The main differential diagnoses included myxoid liposarcoma, spindle cell lipoma and cellular angiofibroma. FISH was negative for DDIT3; moreover, no evidence of regional gain or loss of RB1 was identified by FISH. Based on morphological, immunohistochemical and cytogenetic/molecular findings, a final diagnosis of "lipoblastoma-like tumor" of the inguinal region was rendered.

Non-cutaneous syncytial myoepitheliomas are identical to cutaneous counterparts: a clinicopathologic study of 24 tumors occurring at diverse locations

AIMS

Cutaneous syncytial myoepithelioma (CSM) is a rare myoepithelioma variant of skin, characterized by intradermal syncytial growth of spindle cells with a distinct immunophenotype of EMA and S100 positivity and infrequent keratin expression. While CSM was first described as a cutaneous tumor, singular non-cutaneous cases have since been reported in bone. We aimed to investigate the clinicopathological features of this variant across all anatomic sites through a large multi-institutional study.

METHODS AND RESULTS

We complied a total of 24 myoepitheliomas with syncytial growth from our files. The tumors occurred in 12 male and 12 female patients (M:F = 1:1), with a median age of 31 years (range, 9-69 years). While the majority of tumors (75%, n = 18) occurred in skin, a significant subset (25%, n = 6) arose in non-cutaneous sites, including bone (n = 3), bronchus/trachea (n = 2), and interosseous membrane of tibia/fibula (n = 1). Tumor size ranged from 0.4 to 5.9 cm. Clinical follow-up (7 patients; range 14-202 months; median 56.5 months) showed a single local recurrence 8 years after incomplete skin excision but no metastases; all patients were alive at the time of last follow-up without evidence of disease. Histologically, all tumors were pink at low-power and characterized by a syncytial growth of bland ovoid, spindled, or histiocytoid cells with eosinophilic cytoplasm and prominent perivascular lymphoplasmacytic inflammation. One-third displayed adipocytic metaplasia (8/24). Rare cytologic atypia was seen but was not associated with increased mitotic activity. All tumors expressed S100, SMA, and/or EMA. Keratin expression was absent in most cases. Molecular analysis was performed in 16 cases, all showing EWSR1-rearrangments. In total, 15/15 (100%) harbored an EWSR1::PBX3 fusion, whereas 1 case EWSR1 FISH was the only molecular study performed.

CONCLUSION

Syncytial myoepithelioma is a rare but recognizable morphologic variant of myoepithelioma which may have a predilection for skin but also occurs in diverse non-cutaneous sites. Our series provides evidence supporting a reappraisal of the term "cutaneous syncytial myoepithelioma," as 25% of patients in our series presented with non-cutaneous tumors; thus, we propose the term "syncytial myoepithelioma" to aid pathologist recognition and avoidance of potentially confusing terminology when referring to non-cutaneous examples. The behavior of syncytial myoepithelioma, whether it arises in cutaneous or non-cutaneous sites, is indolent and perhaps benign with a small capacity for local recurrence.