IMT is characteristically composed of spindle myoepithelial cell proliferation accompanied by inflammatory infiltrate of plasma cells, lymphocytes and eosinophils. It usually occurs in the soft tissues and viscera of children and young adults. However, proliferative funiculitis (this term was earlier used to denote an IMT involving the spermatic cord) preferentially affects men of middle to advanced age.4–6
IMT may span the entire age range. The clinical presentation depends on the site of origin. In spermatic cord IMT, the presentation is usually a painless scrotal mass of variable duration.
Ultrasonography (US) is the initial imaging modality of choice in a case of scrotal mass that helps to distinguish intratesticular from extratesticular lesion and solid from cystic lesion. Intratesticular lesion has a high likelihood of malignancy, whereas extratesticular lesion is usually benign. Benign conditions such as spermatocele, varicocele, or tuberculosis must be ruled out. MR imaging helps if US is not conclusive. CT can distinguish a spermatic cord tumor from a retroperitoneal process extending in to the scrotum.7
Macroscopically, IMTs can be firm or fleshy with a white or tan cut surface. Calcification, hemorrhage and necrosis are rare. Histologically, IMTs have three basic patterns: a myxoid/vascular pattern, a compact spindle cell pattern and a hypocellular fibrous pattern, which are often seen in combination within the same tumor.8
The myxoid/vascular pattern has a fasciitis-like appearance, with loosely arranged plump spindle cells in a myxoid stroma and a prominent vasculature and its inflammatory infiltrate often contains more neutrophils and eosinophils and fewer plasma cells than in the other two patterns. The compact spindle cell pattern is characterized by a proliferation of spindle cells with a fascicular architecture admixed with numerous plasma cells and lymphocytes in a collagenous stroma, in line with our case. The fibromatosis-like pattern is relatively hypocellular, with elongated spindle cells in a densely collagenous background containing scattered lymphocytes, plasma cells and eosinophils. The spindle cells of IMT are typically uniform and predominantly myofibroblastic in appearance with oval to spindle-shaped vesicular nuclei, small sized nucleoli, and eosinophilic to amphophilic cytoplasm. Atypical mitoses are rare. Fine needle aspiration cytology showing such features may not be conclusive of IMT; excision biopsy is more reliable.
Immunohistochemistry helps to exclude similar tumors like myxofibrosarcoma, inflammatory fibrosarcoma and malignant fibrous histiocytoma from the differential diagnosis. IMTs are usually immunoreactive for vimentin, muscle-specific actin, smooth muscle actin, desmin, anaplastic lymphoma kinase (ALK) and sometimes for cytokeratin or epithelial membrane antigen.1,4
ALK reactivity could be a favorable prognostic indicator in IMT as distant metastasis was not found among ALK-positive lesions.9
According to a recent study, IMT has a similar morphological appearance as that of IgG4-related sclerosing disease, especially in areas with prominent myofibroblastic proliferation mixed with inflammatory cells. ALK expression, which is found commonly in IMT, helps to differentiate it from IgG4-related sclerosing disease.10
IMTs are classified as tumors of intermediate biologic potential by the World Health Organization, due to a tendency for local recurrence and a small risk of distant metastasis.1
The recurrence rate varies by anatomical site, it is 25% for extrapulmonary IMTs.8
The prognosis after complete surgical excision of paratesticular IMT is excellent.11
These cases should be followed up because some tumors may recur when resection is incomplete. Recurrence is more common in multiple intra-abdominal tumors and those in sites where complete surgical resection is difficult. Tumor recurrence is very infrequent after complete surgical resection of a solitary lesion.12
Radical orchidectomy was performed in most of the paratesticular IMTs for suspicion of malignancy. Chakrabarti and Shetty reported radical orchidectomy for a spermatic cord IMT presenting as a stony hard right scrotal mass.13
Yee et al. reported a case of undescended left testis with IMT from left spermatic cord presenting as a left lower abdominal mass which was excised en bloc with left testis.14
Frozen section helps to exclude malignancy prior to performing radical surgery.