|Year : 2015 | Volume
| Issue : 3 | Page : 659
Mucinous tubular and spindle cell carcinoma of kidney: A case report of an unusual tumor
Bal Chander1, Ramesh Bharti2, Kamal Preet1, Prabal Deb3
1 Department of Pathology, Dr. Rajendra Prasad Government Medical College, Kangra, Tanda, Himachal Pradesh, India
2 Department of Surgery, Dr. Rajendra Prasad Government Medical College, Kangra, Tanda, Himachal Pradesh, India
3 Department of Pathology, Armed Forces Medical College, Pune, Maharashtra, India
|Date of Web Publication||9-Oct-2015|
Department of Pathology, Dr. Rajendra Prasad Government Medical College, Kangra, Tanda - 176 001, Himachal Pradesh
Source of Support: None, Conflict of Interest: None
Mucinous tubular and spindle cell carcinoma (MTSCC) is a rare and unusual variant of renal cell carcinoma (RCC). It is important to differentiate this from the other variants particularly papillary RCC since MTSCC is generally low-grade, has low malignant potential and favorable prognosis. We are reporting a 40-year-old female presenting with right flank pain and well-circumscribed renal mass confined to the lower pole. Tumor consisted of tubules and cords separated by pale mucinous material in some areas, whereas other areas showed dense cellularity without significant mucin. The tumor cells were cuboidal or spindle and did not show significant atypical features. The patient underwent nephrectomy and is asymptomatic clinically and radiologically after 2 years.
Keywords: Mucinous tubular and spindle cell carcinoma, renal cell carcinoma, renal papillary carcinoma
|How to cite this article:|
Chander B, Bharti R, Preet K, Deb P. Mucinous tubular and spindle cell carcinoma of kidney: A case report of an unusual tumor. J Can Res Ther 2015;11:659
| > Introduction|| |
Mucinous tubular and spindle cell carcinoma (MTSCC) is a polymorphic renal epithelial tumor composed of low-grade tubular cuboidal cells and spindle cells set within a mucinous stroma. It is a new entity and has been included in the WHO classification of renal tumors for the first time in 2004.  Until date, there are approximately 100 cases described in the literature.
We report another case of this unusual entity in a 40-year-old female along with clinicopathological features.
| > Case report|| |
A 40-year-old female patient presented with pain upper right abdomen of 6 months duration. The pain was mild in intensity, but would exacerbate while bending down and fast walking. Her family history and past medical history was unremarkable except for an appendectomy 10 years back. She has been menopausal for the last 4 years. Her general physical condition was good and vital parameters were within normal range. There was tenderness in the epigastrium and right lumber region. Routine laboratory investigations and renal function tests were within normal limits. Ultrasound showed a well-defined echogenic, hyperechoic, rounded mass in the lower pole of the right kidney, measuring 5 × 5 cm.
Based on the clinical and radiological evaluation, a diagnosis of renal cell carcinoma (RCC) along with epigastric hernia was considered. She was taken up for right nephrectomy and repair of the epigastric hernia. Partial nephrectomy was not opted since the patient belonged to poor socioeconomic status and tribal area, which would have precluded strict follow-up after partial nephrectomy.
On gross examination of the resected right kidney, a grey white well-circumscribed tumor measuring 5.5 cm in diameter was seen in the lower pole. Cut surface showed areas of hemorrhage [Figure 1].
|Figure 1: Gross specimen of nephrectomy specimen: Longitudinal section showing a well circumscribed mass with areas of hemorrhagic and necrosis. The mass is confined to the lower pole of kidney|
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Microscopic sections from the tumor showed a neoplasm composed of tubules and long cords. Most of the tumor cells were cuboidal with focal areas of spindle cells, set within a pale mucinous stroma. [Figure 2] and [Figure 3] Cells did not show significant pleomorphism, increased mitotic activity or necrosis. [Figure 4] Immunohistochemistry showed tumor cells to be positive for CD7. [Figure 5] The cells were negative for WT1 and CD10. Based on these features, a diagnosis of MTSCC was made.
|Figure 2: Low power, H and E stained section of tumor showing tubules and cords composed of oval to spindle cells. The interstitial space show presence of myxoid material|
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|Figure 3: Low power, H and E stained section of tumor showing dense cellularity and scant myxoid material|
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|Figure 4: High power, H and E stained section of tumor. Individual cell nuclei with and without prominent nucleoli. No other atypical features present|
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|Figure 5: Low power, Immunohistochemistry for CD7. The tumor cells are positive|
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| > Discussion|| |
Mucinous tubular and spindle cell carcinoma is a rare and newly described low-grade renal epithelial tumor generally associated with indolent behavior.  Mostly, this entity has been reported in the literature as single case reports and an occasional case series.
The tumor is more prevalent among adults with a mean age of 53 years (range: 17-82), with a marked female preponderance (1:4). Clinically, they are generally asymptomatic or present with flank pain or hematuria and are detected on ultrasonography. The age and sex, and clinical presentation of the present case was similar to that described in the literature. 
The issue of origin of MTSCC is still unsettled. Expression of epithelial markers namely; alpha-methylacyl-coenzyme A racemase (AMACR), epithelial membrane antigen (EMA), CK7 and vimentin has been reported in 80-100% of the cases thus supporting a possible origin from distal convoluted epithelial cells.  However, AMACR expression can also be seen in proximal convoluted cells leading to the belief that it could be a variant of papillary RCC. This is further supported by overlapping immunohistochemical profile of these two tumors. 
Macroscopic evaluation of the resected kidney generally shows a well-circumscribed, gray to tan colored tumor with or without areas of hemorrhage or necrosis, akin to that noted in the index case.
Histopathological evaluation is imperative to exclude the clinicoradiological suspicion of RCC. A typical case of MTSCC is composed of low-grade cuboidal cells arranged in microtubules and long cords making abrupt transitions to spindle morphology. These structures are arrayed in a mucinous or myxoid stroma that reacts strongly with alcian blue. Nuclear atypia and mitoses are rare in both cuboidal and spindle cells. Because of the presence of compact tubular architecture, focal papillations and mucin production, the MTSCC has some morphological similarities with papillary RCC, particularly type 1, 2 apart from extracellular mucin, presence of which is rare or absent in the latter neoplasm. This tumor may mimic papillary RCC associated with sarcomatoid change. However, MTSCC with spindle cells arranged in parallel bundles with eosinophilic cytoplasm and low-grade nuclei, aids in morphological recognition of this uncommon tumor. 
Despite its rarity, isolated case reports have noted various atypical histological features of this neoplasm. MSTCC may have "mucin-poor" background, predominance of spindle cell component, psammomatous calcification, features of anapalsia suggestive of "high-grade", or sarcomatous change heralding metastasis into the lymph node or to distant organ.  Sarcomatoid change has been reported to be associated with aggressive behavior. These areas are identified by pleomorphic, bizarre nuclei, prominent nucleoli, and presence of necrosis. These areas have been further shown to have increased MIB1 expression with the loss of CK7 and AMACR expression. 
Immunohistochemistry is not helpful in discriminating between papillary RCC and MTSCC. The histomorphological features alone appear to be the gold standard for making the diagnosis. However, the immunoreactive pattern of MTSCC appears to be complex with expression of low molecular weight keratin (CAM5.2, MAK6), CK7, CK18, CK19, EMA, vimentin and CD15, and immunonegativity for CD10 and villin. ,, The case we are presenting showed positivity for CD7 and negativity for WT1 and CD10.
Despite its low-grade morphology, which generally is associated with an indolent behavior, an occasional case histological lacking features of anaplasia exhibited behavior of a high-grade tumor, in the form of local or distant metastasis.
The genes and molecular pathways underlying MTSCC are yet to be completely explored. Kuroda et al. performed comparative genomic hybridization analysis of a case of high-grade MTSCC that showed gain of chromosomes 1q, 7, 16, 19q, and Y and loss of chromosomes 1p, 6p, 8p, 11q (del (11)(q23)), and 13. Subsequent G-band karyotyping of the same case showed gain of chromosomes 2, 5, 7, 12, 16, and 20 and loss of chromosome 15.  Cossu-Rocca et al. have reported that MTSCC lacks the gain of chromosomes 7 and 17 and loss of chromosome Y as seen in papillary RCC.  Deletions of von Hippel-Lindau (VHL) gene have not been observed. The prognosis is generally considered to be favorable.  Although available data is preliminary, yet we can infer that there is no involvement of chromosome 3 or VHL gene and hence the pathways involved in conventional clear cell RCC are unlikely to be involved in MTSCC. This also may imply that the currently used drugs like tyrosine kinase inhibitors and mTOR inhibitors may not be as effective in this subset of patients as they are in conventional RCC. As more information about the involved pathways is generated, the use of targeted therapy can be validated in these patients. There is no available data showing it to be hereditary in nature to the best of our knowledge.
Thus, though MTSCC is considered to be a low-grade neoplasm, but owing to the occasional cases with high-grade behavior, all such cases should be kept under surveillance during the postoperative period, until a better understanding of the biology of this rare tumor is obtained. Apropos present case the patient is asymptomatic for the last 2 years after nephrectomy.
The aim of this case report was to highlight an uncommon neoplasm, which can be reliably diagnosed based on its distinctive morphology, without the need of elaborate ancillary techniques. Further, pathologists should consider the possibility of this neoplasm while dealing with renal tumors since this is associated with a more favorable prognosis.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]