mucinous cystic tumors of the ovary rarely contain one or more solid mural nodules in which the histological features differ markedly from the background of benign , borderline or malignant mucinous neoplasms . four varieties of mural nodules have been described , including true sarcomas , sarcoma - like mural nodules ( slmn ) , foci of anaplastic carcinoma and mixed type . slmn stend to occur in younger women and are characterized by smaller size , sharp demarcation , a heterogeneous cell population , and no serious impact on the prognosis . it should be differentiated from true sarcomatous mural nodules and foci of anaplastic carcinoma with areas of sarcomatoid differentiation since both of these lesions carry a graver prognosis . we report a very rare case of slmn in a borderline mucinous tumor of the ovary . a 30-year - old unmarried female patient presented with progressive abdominal enlargement for last 7 months . she also complained of mild lower abdominal pain and discomfort for last 2 and half months . a cystic swelling of about 18 - 20 weeks size reaching just below the level of umbilicus was felt on physical examination . ultrasonography revealed a left ovarian cystic space - occupying lesion(sol ) of 12 cm  9.6-cm size with internal echogenicity and septations . grossly the cystic ovarian mass [ figure 1a ] measured 13.8 cm  12 cm  8 cm . an elevated firm , well - definednodular area measuring 4.8 cm  3.6 cm  2.5 cm was noticed on the inner surface of the largest locule . microscopic examination displayed the histopathological features of a borderline mucinous tumor showing complex cribriform architecture with mild to moderate cellular atypia along with an adjacent circumscribed nodular area [ figure 1b and d ] . however , no recognizable glandular structures infiltrating into the deeper part of the nodule were identified . the nodular area was predominantly composed of pleomorphic spindle cells with hyperchromatic nuclei and occasional prominent nucleoli arranged in a vaguely fascicular pattern . the pleomorphic cells focally demonstrated smooth muscle and rhabdomyoblastic differentiation [ figure 2a and b ] . frequent mitotic figures including atypical forms admixed with histiocytes and inflammatory cells especially eosinophils were noticed . immunohistochemistry for cytokeratin was focally positive and vimentin was diffusely positive in the pleomorphic spindle cells of the nodule . overall , the histopathogical features of the nodule closely mimicked that of a sarcoma except the presence of circumscription and absence of vascular invasion . true sarcoma , atypical inflammatory myofibroblastic tumor , carcinosarcoma were considered as differential diagnoses . however , considering the circumscription of the nodule in macroscopy as well as in microscopy along with corroborative histopathological and immunohistochemical findings , the diagnosis of a borderline mucinous tumor with slmn was made . ( a ) mucinous cystic neoplasm of ovary with mural nodule ( b ) a well - circumscribed slmn alongwith borderline mucinous tumor ( h and e , 100 ) ( c ) a cellular well - demarcated nodular area of slmn ( h and e , 100 ) ( d ) complex atypical cribriform glands of borderline mucinous neoplasm ( h and e , 400 ) ( a ) photomicrograph showing prominent mitotic figures and smooth muscle differentiation in slmn ( h and e , 400 ) ( b ) rhabdomyoblastic differentiation in slmn ( h and e , 400 ) ( c ) photomicrograph showing coagulative necrosis in slmn ( h and e , 400 ) ( d ) atypical mucinous glands showing strong cytokeratin positivity and spindle cells of the nodule in the background displaying focal and weak cytokeratin positivity ( h and e , 100 ) in 1979 , prat and scully reported 14 cases of slmns , seven of them from the previous literature , and pointed outtheir favorable clinical behavior . they described three types of morphology in slmns namely pleomorphic and epulis type , pleomorphic and spindle cell type and giant cell - histiocytic type . sarcomatous nodules can exhibit a variety of patterns , including fibrosarcoma , rhabdomyosarcoma , and undifferentiated sarcoma . mixed nodules may feature carcinosarcoma or a mixed anaplastic carcinoma and sarcoma - like nodule . the present case displayed the morphology similar to the pleomorphic and spindle cell type with areas of smooth muscle and rhabdomyoblastic differentiation . in contrast to slmns , the sarcomatous nodules and foci of anaplastic carcinoma which can also present as mural nodule , tend to occur in older patients and are characterized by larger size , poor circumscription , a monotonous spindle cell population in the former , evidence of carcinomatous differentiation in the latter , and aggressive behavior . anaplastic carcinomatous nodules generally have spindled and rhabdoid cells with unequivocal cytologic features of a high - grade malignancy , and are associated with intraepithelial or invasive mucinous carcinoma in 72% of cases . atypical inflammatory myofibroblastic tumors may resemble slmns possibly due toa florid reaction to intramural hemorrhage or spilling of mucinous material in cystic ovarian tumors . in contrast to slmns that occur in association with an epithelial tumor , inflammatory myofibroblastic tumors have a predilection for relatively younger patients , appear de novo , and are larger and less well circumscribed . although various hypotheses have been proposed to explain the histogenesis of the slmns , it probably represents a reactive and self - limited phenomenon within a neoplasia . slmns usually strongly express vimentinand focally or weakly express cytokeratin , similar to true sarcomas yet distinct from anaplastic carcinomas that usually have strong / diffuse cytokeratin expression . finally the age of the patient , well circumscription of the nodule and lack of vascular invasion were the only parameters that led us to the correct diagnosis . the outcome of mucinous tumors with slmns is the same as the corresponding category of mucinous tumors without the nodule . but slmns should be regarded with caution as their histologic appearance is worrisome and clinical follow - up data are very limited . hence , careful and meticulous examination of this rare lesion within a mucinous cystic tumor is essential for reassuring the patient of a favorable clinical outcome and for excluding the similar looking aggressive lesions having poorer outcome .