Pathologic quiz case. Vaginal wall mass in a 47-year-old woman. Vaginal rhabdomyoma.

Abstract

A 47-year-old white woman presented with postmenopausal uterine bleeding while on hormone replacement therapy. The patient did not complain of dyspareunia or postcoital vaginal bleeding. The patient's past medical history was significant for metrorrhagia in 1998. An endometrial biopsy, performed at that time, revealed late secretory/menstrual-type endometrium. The current postmenopausal bleeding was evaluated by transvaginal ultrasound, which revealed polypoid lesions in the endometrial cavity. During hysteroscopy and dilatation and endometrial curettage, a small vaginal wall nodule was noted; this nodule was excised.The hematoxylin-eosin–stained sections of the curettage showed endometrial polyps and weakly proliferative endometrium. The vaginal wall mass was a single mucosa-covered, ovoid, tan, rubbery, and firm nodule, which measured 0.8 × 0.7 × 0.5 cm. Light microscopic examination revealed nonkeratinizing squamous epithelium consistent with vaginal mucosa (Figure, A). The subepithelial stroma contained large strap-shaped cells arranged in a vague fascicular pattern (Figure, B). These cells had a low nucleocytoplasmic ratio with small vesicular nuclei. The nuclei showed little polymorphism; no mitotic figures were noted. The cytoplasm was abundant and eosinophilic. Cross-striations were identified in some of these cells (Figure, C).What is your diagnosis?Rhabdomyomas are tumors containing striated muscle cells and are divided into cardiac and extracardiac types. The extracardiac type generally is divided further into 3 subgroups, namely adult, fetal, and genital rhabdomyomas. Both adult and fetal rhabdomyomas tend to be found in the head and neck. The adult rhabdomyomas tend to present at an average age of 50 years and contain cells with cytoplasmic vacuoles but without easily observable cross-striations on hematoxylin-eosin staining. The fetal rhabdomyomas tend to be found in children, although they have been found in older adults, and consist of immature skeletal muscle fibers.1 Genital rhabdomyomas are rare tumors; 27 cases have been reported in the vagina, 3 in the vulva, and 3 in the portio/cervix.2,3 Vaginal rhabdomyomas may present as a mass, either as an incidental finding on examination (as in the current case) or associated with vaginal bleeding or dyspareunia. Vaginal rhabdomyomas have been described in women between 25 and 54 years of age (median age of 42 years).Gross examination of vaginal rhabdomyomas usually reveals a firm, lobulated, polypoid lesion measuring approximately 2 to 3 cm and covered by a smooth epithelial surface.3,4 No ulceration or hemorrhage is typically observed. Microscopically, the lesions are typically covered by normal nonkeratinizing squamous epithelium. Underlying the epithelium there is loose connective tissue with evenly distributed fibroblasts and dilated thin-walled capillaries. The stroma contains interlacing fascicles or bundles of polymorphous cells, which include small cells with scant cytoplasm, spindled cells, polygonal cells, or strap-shaped cells. Many of the cells have eosinophilic cytoplasm with cross-striations, and the nuclei are usually bland with no mitoses. On electron microscopy, thick and thin myofilaments with A, I, and H bands and prominent Z lines have been observed.5,6 Immunohistochemical staining further demonstrates that the tumor cells are rhabdomyoblasts that stain positively for desmin, myoglobin, actin, and myosin,2,7 and that the tumor cells are surrounded by basement membrane laminin and type IV collagen.8Vaginal rhabdomyomas are benign lesions that are typically treated with excision alone. After excision, patients are typically asymptomatic.6 Recurrences are rare, with only 1 reported case following excision; no metastases have been reported.3,6,9The differential diagnoses of the vaginal rhabdomyomas include vaginal polyps and sarcoma botryoides. Vaginal polyps tend to have a clinical presentation similar to that of vaginal rhabdomyoma, but contain pleomorphic stromal cells that have 1 or more nuclei and lack the cross-striated muscle cells. Sarcoma botryoides is a malignant neoplasm that usually occurs in children younger than 8 years. It has a gross appearance of grapelike vesicles with frequent ulceration of the epithelium. Sarcoma botryoides has a classic cambium layer, primitive mesenchymal stroma, nuclear polymorphism, and mitotic figures.1,4,6The histogenesis of vaginal rhabdomyomas is not well understood. It has been proposed that the lesions represent a maturation of an embryonal rhabdomyosarcoma, but it is unlikely, as it would be expected to occur in an earlier age range with a transitional appearance between that of embryonal rhabdomyosarcoma and rhabdomyoma. The maturation hypothesis is also unlikely, as several of the case reports included patients who had had previous pregnancies with no noted vaginal lesions before discovery of the vaginal rhabdomyomas.3,4 Some investigators have also proposed that vaginal rhabdomyomas are hamartomas rather than true neoplasms, but the lesions would be expected to present in a younger age group as well.4 In conclusion, although the histogenesis of vaginal rhabdomyomas is yet to be determined, the reported cases indicate that they are rare, benign, polypoid lesions containing well-differentiated striated muscle, and that they rarely recur after excision.