Inflammatory myofibroblastic tumor of the pituitary: A case report

Open access: https://ina-jns.org/ Inflammatory myofibroblastic tumor of the pituitary: A case report Saurabh Sharma1*, Laila Sivanandapanicker Jyothish1, Raja Kutty1, Anil Kumar Peethambaran1, Milesh Nagar1, Sourabh Jain


INTRODUCTION
Inflammatory Myofibroblastic Tumors of Central Nervous System (IMT-CNS), have been reported in literature sporadically over the last few decades, but their presence in the pituitary gland was first reported in 2001. Although the pulmonary system is the most frequently involved site, the CNS, gastrointestinal tract, tonsils, urogenital tract, heart, and orbit may also be affected. Concomitant involvement, such as that of the lung and CNS, might be encountered as well. Only a few cases of Inflammatory Myofibroblastic Tumors of the pituitary gland (IMT-Sella) have been reported.
We discuss a case of pituitary IMT that mimicked pituitary macroadenoma but was later diagnosed on histopathology. The objective of our case report is to analyze the basis of their mimicry, discuss their differential diagnosis and review the literature for their behaviour, management protocols and prognosis by searching PubMed using the keywords such as "inflammatory myofibroblastic tumor", "plasma cell granuloma", "inflammatory pseudotumor", "pituitary" and references cited in identified PubMed articles.

CASE PRESENTATION
A 45-year-old male presented with complaints of moderate to severe intensity, bifrontal headache for two months and blurring of vision in the temporal side of visual filed since two weeks ago. Neurological examination revealed bitemporal hemianopsia. His blood work was suggestive of panhypopituitarism. The patient was evaluated radiologically, and MRI revealed a large well defined T1 hyperintense lesion involving sella extending to the suprasellar region. The lesion measured 2 x 2.1 x 1.6 cm. It appeared hyperintense in T1W1 and hyperintense in STIR with small hypointense areas. The lesion had multiple CSF signal intensity areas suggestive of cystic change. The T2W1 lesion had well defined peripheral hyperintense rim. The lesion extended into the suprasellar region. The optic chiasm appeared compressed by the mass lesion. Laterally, on the left side of the lesion was seen encasing the internal carotid artery (Figure 1).
A working diagnosis of pituitary adenoma was made, and the patient was taken up for endonasal endoscopic transsphenoidal total excision of pituitary adenoma. Intraoperatively, the tumor was firm to hard in consistency, grey-white in color and moderately vascular. In the post-op period, there were no complications such as CSF leak, bleeding, diabetes insipidus, and neurological deficit. It was uneventful, and the patient was relieved of his symptoms.
The histopathology revealed neoplasm composed of spindle-shaped cells arranged in short bundles. Individual cells were found to be spindly with a moderate amount of eosinophilic    cytoplasm and elongated nuclei with tapered edges. Sprinkled in between these were epithelioid cells and lymphocytes. RBC's along with hemosiderinladen macrophages, respiratory epithelium lined tissue, and few areas of necrosis were also noted ( Figure 2). Immunohistochemistry of spindle cells was positive for Smooth Muscle Actin (SMA), Vimentin, negative for Anaplastic Lymphoma Kinase (ALK), CD1(a) and S100 (Figure 3 and 4).
Histological diagnosis of IMT was made. On discharge, the patient was given a course of corticosteroids. Six months post-surgery, repeat MRI revealed no residual/recurrent tumor.

DISCUSSION
IMT is an arcane inflammatory pseudotumor first described by Bahadori and Leibow in 1973. 1 Eventually it was found to be ubiquitous occurring commonly in the lung, omentum, mesentery and urinary bladder of children and young adults. 2 IMT-CNS is a rare entity, with only 100 cases being reported so far. 3 Most tumors arise from meningeal structures, though intracerebral and intraventricular lesions have been known to occur. 4 From our literature search, only 7 cases of intrasellar IMT have been reported until now (Table 1). [5][6][7][8][9][10][11] The scarcity of literature available on intrasellar IMT compelled us to extrapolate data from the cases, occurring in other areas of the central nervous  (Table 2) Etiopathogenesis of IMT remains unascertained with the ongoing debate between infective and autoimmune pathology. Clinically, IMT-Sella presents with features of headache, vision problems and hypopituitarism. Differential diagnoses of pituitary IMT are pituitary adenomas, inflammatory and granulomatous lesions of pituitary, meningioma and lymphomas. Radiologically, IMT-Sella appears hyperattenuated on CT and homogenous hypointense lesions on T2 weighted images because of the lack of mobile protons in the fibrotic background. 9 On histopathology, IMT is a unique lesion composed of myofibroblastic spindle cells accompanied by inflammatory cells. 15 (Table  1). This clearly highlights the histopathological differences between the two entities, though its impact on disease progression cannot be stated,  Immunohistochemically, these tumors are positive for SMA, muscle-specific actin, vimentin in up to 90% cases, desmin in up to 70% cases and negative for myogenin, S100 and Homatropine Methylbromide 45 (HMB45). In situ hybridization of FHC variant may often show clonal rearrangement in chromosome 2p23 leading to activation of the ALK gene. It has been reported that those IMT-CNS, which express ALK, have an aggressive course and are associated with high recurrence rates. 16 Treatment modalities considered for IMT-CNS are surgical resection, corticosteroid therapy, radiotherapy and immunosuppressive therapy with ALK inhibitors. Treatment patterns mentioned in the literature and the present review are elaborated in Table 3. According to all of these studies, total surgical excision if achieved without much morbidity is the best modality. Corticosteroid therapy can be considered to avoid considerable surgical risk, especially in PCG like variants, which respond better to corticosteroid therapy than FHC variants. 6 One recurrence and no cases of malignant transformation were noted in our study, although the average follow-up time was just 20 months, and maximum follow-up was carried out only for 3 years. Recurrence rates of 12.5% to 40% in IMT-CNS cases have been noted in the literature. 17 (Table 3) Gallago et al. studied all cases of recurrence in IMT-CNS and found 19 such instances in over 100 cases reviewed. 3 Going through their data, we noted that the PCG variants had higher chances of recurrence than the FHC variants, and 11 out of 19 (57.8%) patients were females. Twelve of the cases (63%) who showed recurrence had not undergone gross total resection as their primary modality of management. The average time until recurrence for CASE REPORT patients who underwent complete resection was 37 months, while the average time until progression/ recurrence for the rest of the cases was 29 months. Hausler et al. also noted that the female gender and incomplete resection were independent risk factors for recurrence. 4 Similarly, in our review, the only recurrence noted was in a female patient with incomplete resection. 6

CONCLUSION
IMT-Sella is a rare neoplasm at a rare location. Histopathologically, these are FHC variant predominant lesions as compared to other CNS locations. Total surgical resection should be the target goals for treatment of all IMT. In case of difficult surgical access and contraindication to surgical procedures, treatment with corticosteroids can bring good results. The presence of PCG variant, female gender and incomplete resection are poor prognostic factors. It is important to differentiate the histopathological variant, so an early assessment can be made regarding the aggressiveness and malignant potential of the tumor and appropriate further management.

FUNDING
No funding accepted.