A tale of two clones: Caldesmon staining in the differentiation of cutaneous spindle cell neoplasms

Leiomyoma and Leiomyosarcoma (Primary and Metastatic) of the Oral and Maxillofacial Region: A Clinicopathological and Immunohistochemical Study of 27 Cases

Smooth muscle neoplasms represent an important group of lesions which is rare in the oral cavity. Leiomyoma (LM) is benign smooth muscle/pericytic tumor usually presenting as non-aggressive neoplasm, while leiomyosarcoma (LMS) represents its malignant counterpart. The rarity of these lesions, together with its unspecific clinical presentation and a variable histopathological appearance, lead to a broad list of differential diagnoses, hampering their diagnoses. Therefore, in this study we describe the clinical and microscopic features of a series of oral and maxillofacial LMs and LMSs. A retrospective search from 2000 to 2019 was performed and all cases diagnosed as LM and LMS affecting the oral cavity and gnathic bones were retrieved. Clinical and demographic data were obtained from the patients' pathology records, while microscopic features and immunohistochemistry were reviewed and completed when necessary to confirm the diagnoses. Twenty-two LMs and five LMSs were obtained. In the LM group, males predominated, with a mean age of 45.7 years. The upper lip was the most affected site, and 18 cases were classified as angioleiomyomas and four as solid LM. In the LMS group, females predominated, with a mean age of 47.6 years. The mandible was the most affected site. Diffuse proliferation of spindle cells, with necrosis and mitotic figures, were frequent microscopic findings. LMs and LMSs were positive for α-smooth muscle actin, HHF-35 and h-caldesmon. In conclusion, oral LM/LMS are uncommon neoplasms with the latter usually presenting as metastatic disease. H&E evaluation may be very suggestive of oral LMs, but h-caldesmon staining is strongly recommended to confirm LMS diagnosis.

"Inflammatory Leiomyosarcoma" and "Histiocyte-rich Rhabdomyoblastic Tumor": a clinicopathological, immunohistochemical and genetic study of 13 cases, with a proposal for reclassification as "Inflammatory Rhabdomyoblastic Tumor"

Inflammatory leiomyosarcoma (ILMS), defined as "a malignant neoplasm showing smooth muscle differentiation, a prominent inflammatory infiltrate, and near-haploidization", is a very rare soft tissue tumor with a generally favorable prognosis. The morphologic features of "histiocyte-rich rhabdomyoblastic tumor" (HRRMT) are similar to those of ILMS, although this lesion shows by definition a skeletal muscle phenotype. Recent gene expression profiling and immunohistochemical studies have also suggested that ILMS and HRRMT may be related. We studied the clinicopathologic, immunohistochemical and genetic features of four cases previously classified as ILMS and nine classified as HRRMT. Tumors from both groups tended to occur in the deep soft tissues of the extremities of young to middle-aged males and exhibited indolent behavior. Morphologically, all were well-circumscribed, often encapsulated, and showed a striking histiocyte-rich inflammatory infiltrate admixed with variably pleomorphic tumor cells showing spindled and epithelioid to rhabdoid morphology, eosinophilic cytoplasm, and prominent nucleoli, but few, if any, mitotic figures. Immunohistochemically, the tumor cells expressed desmin, alpha-smooth muscle actin, and the rhabdomyoblastic markers PAX7, MyoD1, and myogenin. H-caldesmon expression was absent in all cases, using the specific h-CD antibody. Karyotypic study (1 HRRMT) and genome-wide copy number analysis (7 HRRMT, OncoScan SNP assay), revealed near-haploidization in four cases, with subsequent genome doubling in one, an identical phenotype to that seen in ILMS. We propose reclassification of ILMS and HRRMT as "inflammatory rhabdomyoblastic tumor", a name which accurately describes the salient morphologic and immunohistochemical features of this distinctive tumor, as well as its intermediate (rarely metastasizing) clinical behavior.

Leiomyosarcoma of the skin: review of the literature with an emphasis on prognosis and management

Leiomyosarcoma (LMS) of the skin is rare, and no management guideline currently exists. Although LMS is historically classified as either dermal (cutaneous) or subcutaneous, definition for its classfication is inconsistent in the literature. Studies on the managenent of LMS are scarce, and there is no consensus on the appropriate surgical margin for the treatment of LMS. While a 1 cm margin may be sufficient in cutaneous LMS, wider margins may be required for subcutaneous tumors. Mohs micrographic surgery is a promising surgical modality for the treatment of cutaneous LMS. In this review, current knowledge on LMS is summarized and a practical approach to the management of this rare neoplasm is proposed.