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  Table of Contents    
LETTER TO EDITOR  
Year : 2017  |  Volume : 60  |  Issue : 1  |  Page : 133-135
Tumor-to-tumor metastasis: Small cell carcinoma lung metastasising into a follicular adenoma of the thyroid


1 Department of Histopathology, Postgraduate Institute of Medical Education and Research, Sector 12, Chandigarh, India
2 Department of ENT, Postgraduate Institute of Medical Education and Research, Sector 12, Chandigarh, India

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Date of Web Publication14-Feb-2017
 

How to cite this article:
Gowda KK, Bal A, Agrawal P, Verma R, Das A. Tumor-to-tumor metastasis: Small cell carcinoma lung metastasising into a follicular adenoma of the thyroid. Indian J Pathol Microbiol 2017;60:133-5

How to cite this URL:
Gowda KK, Bal A, Agrawal P, Verma R, Das A. Tumor-to-tumor metastasis: Small cell carcinoma lung metastasising into a follicular adenoma of the thyroid. Indian J Pathol Microbiol [serial online] 2017 [cited 2017 Sep 25];60:133-5. Available from: http://www.ijpmonline.org/text.asp?2017/60/1/133/200037


Editor,

Tumor-to-tumor metastasis is a rare phenomenon with 150 cases documented in the English literature till date. The commoner recipients include renal cell carcinoma, meningioma, and thyroid neoplasms, while carcinomas of lung, breast, stomach, prostate, and thyroid are the common donor tumors.[1] Amongst thyroid neoplasms serving as a recipient, follicular adenoma is the commonest benign thyroid neoplasm with papillary carcinoma thyroid being the commonest malignant thyroid neoplasm.[1]

We report the first case of a small cell carcinoma lung metastasizing to a follicular adenoma of the thyroid gland. A 52 year old male presented with complaints of persistent cough and shortness of breath of 6 months duration. Routine investigations for infections such as sputum smear and cultures were negative. Serial sputum cytology screening was negative for malignancy. Imaging studies revealed a mass in the right upper lobe of the lung measuring 5. 5 cm × 5. 0 cm × 4. 5 cm. A transbronchial lung biopsy was performed which on histology revealed a small cell carcinoma. The tumor cells were positive for neuroendocrine markers like synaptophysin (SNP), and CD56 [Figure 1]. Based on the biopsy report the patient was subjected to chemo-radiotherapy with cisplatin and etoposide.
Figure 1: Transbronchial lung biopsy shows: (a) tumor with tumor cells displaying high nuclear.cytoplasmic ratio and high mitotic count. (H and E, ×400). (b) The tumor cells are positive for CD56, a specific neuroendocrine marker confirming the tumor to be small cell carcinoma. (×400)

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The patient improved symptomatically and was kept on regular follow-up. One year later the patient presented to the otorhinolaryngologist with a midline thyroid swelling in the neck of 25 years duration with a recent increase in size. On examination a 6 cm × 6 cm firm, non-tender nodule was noted in the left lobe of thyroid gland which moved with deglutition. CECT showed a hyperdense lesion with necrosis and calcification corresponding to the nodule [Figure 2]. Fine needle aspiration cytology of the nodule was reported as papillary thyroid carcinoma. Subsequently the patient underwent total thyroidectomy.
Figure 2: CT scan showing a tumour with areas of calcification

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Grossly the thyroid specimen measured 14 cm × 8 cm × 3 cms, with an encapsulated nodule measuring 6 cm × 6 cm × 3cms in the left lobe of the thyroid gland. On cut surface the nodule was solid, tan brown in color with grey white areas of fibrosis and calcification. In addition, numerous discrete grey lesions 2-5 mm in size were noted within the nodule [Figure 3]a. Microscopic examination revealed a follicular adenoma with no capsular breach or vascular invasion. The areas corresponding to the grey lesions showed discrete clusters of small cells with high nuclear-cytoplasmic ratio and hyperchromatic nuclei. In contrast to other areas of follicular adenoma, these clusters showed brisk mitotic activity. There was complete lack of reaction (desmoplastic, inflammatory or myxoid) of the recipient tumor to the metastatic deposits. The cells in these clusters were positive for CD56 and SNP while CK, TGB, TTF1, calcitonin and vimentin were negative [Figure 3]b, [Figure 3]c, [Figure 3]d. Based on these findings a diagnosis of metastatic small cell carcinoma to a follicular adenoma of the thyroid was made.
Figure 3: (a) Gross photograph shows the cut surface of a well encapsulated lesion with numerous discrete white areas being well made out. (b) The whitish areas on microscopy represented metastatic deposits of small cell carcinoma of lung (H and E, ×400). (c and d) The metastatic tumor cells are positive for CD56 and Synaptophysin, while the follicular epithelial cells are negative for the same immunostains (×400)

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Tumor-to-tumor metastasis is a rare phenomenon. The diagnosis requires certain criteria to be fulfilled. It is essential that the recipient tumor is a true neoplasm and that the donor neoplasm is a true metastasis. The invasion into the recipient neoplasm should be proven beyond doubt, with the presence of only tumor emboli within a recipient neoplasm being excluded from such a diagnosis. This also excludes collision tumor, contiguous growth of one neoplasm into another adjacent neoplasm, and metastases to a lymph node already involved by a lymphoreticular malignancy.[1] Our case of a small cell carcinoma lung metastasizing into a follicular adenoma of the thyroid gland meets all the criteria of a tumor to tumor metastasis. On intial pathology examination, these small metastatic foci in a background of follicular adenoma were overlooked and taken as proliferation of follicular epithelial cells both on gross and microscopic examination. Thus this requires meticulous pathology examination.

Tumor metastasis is in itself a multifactorial process, and therefore the mechanisms of tumor to tumor metastasis are also complex and largely unknown with two theories being proposed. First is the mechanical theory which suggests that the development of metastasis depends on the number of viable tumor cells reaching an organ or a recipient neoplasm.[2] Second theory, which is the most accepted is the seed and soil theory given by Sir Steven Paget in 1889. It hypothesizes that tumor or metastasis development occurs when a compatible environment (the soil) is provided to viable tumor cells (the seed). Based on this the biochemical properties of renal cell carcinoma, such as high cytoplasmic lipid and glycogen content, favours growth of tumor cells, which is why it acts as one of the commoner recipient tumors.[3] The first case of tumor to tumor metastasis was reported by Berent et al.[4] in 1902, in which a 58 year old Caucasian male with squamous cell carcinoma of the lower jaw had tumor to tumor metastasis in a renal cell carcinoma. Thereafter, there have been about 150 such case reports.[2] The common recipients include renal cell carcinoma, meningioma, and thyroid neoplasm while carcinomas of lung, breast, stomach, prostate, and thyroid are the common donor tumors.[2]

Metastasis to thyroid gland is uncommon and ranges from 0.5% in an autopsy series to 24% in cases with widespread metastases. Metastasis to a primary thyroid neoplasm is rare. According to Stevens et al.,[1] only 28 such cases have been documented so far. The following features were present in the majority of the metastatic neoplasms: multifocality of the metastatic tumor aggregates; a total lack of, or only minimal amounts of reaction (desmoplastic, inflammatory or myxoid) of the recipient tumor to the metastatic deposits; and retention of the histopathologic characteristics of the donor tumor in the metastatic deposits.[3] Amongst thyroid neoplasms serving as a recipient, follicular adenoma is the commonest benign thyroid neoplasm with papillary carcinoma thyroid being the commonest malignant thyroid neoplasm. Among the neoplasms metastasising to a primary thyroid neoplasm, renal cell carcinoma is the most common (9/28), followed by lung (6/28), breast (5/28), and colon (3/28) carcinoma.[1] Adenocarcinomas are the commonest lung carcinomas metastasizing to primary thyroid neoplasms followed by squamous and large cell carcinomas.[5] There has been only one case of a small cell carcinoma of lung metastasizing to follicular variant of papillary thyroid carcinoma. till date by Baloch et al.[6] To the best of author's knowledge, this is the first ever case report of small cell carcinoma lung metastasising to follicular adenoma of thyroid gland.

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Conflicts of interest

There are no conflicts of interest.

 
   References Top

1.
Stevens TM, Richards AT, Bewtra C, Sharma P. Tumors metastatic to thyroid neoplasms: A case report and review of literature. Patholog Res Int 2011;2011:238693.  Back to cited text no. 1
    
2.
Kameyama K, Kamio N, Okita H, Hata J. Metastatic carcinoma in Follicular Adenoma of the Thyroid Gland. Pathol Res Pract 2000;196:333-6.  Back to cited text no. 2
    
3.
Fadare O, Parkash V, Fiedler PN, Mayerson AB, Asiyanbola B. Tumor to tumor metastasis to a thyroid follicular adenoma as the initial presentation of a colonic adenocarcinoma. Pathol Int 2005;55:574-9.  Back to cited text no. 3
    
4.
Campbell LV Jr., Gilbert Enid, Chamberlain CR Jr, Watne AL. Metastases of Cancer to Cancer. Cancer 1968;22:635-43.  Back to cited text no. 4
    
5.
Katsenos S, Archondakis S, Vaias M, Skoulikaris N.. Thyroid gland metastasis from small cell lung cancer: An unusual site of metastatic spread. J Thorac Dis 2013;5:E21-4.  Back to cited text no. 5
    
6.
Baloch ZW, Livolsi VA. Tumor-to-tumor metastasis to follicular variant of papillary carcinoma of thyroid. Arch Pathol Lab Med 1999; 123:703-6.  Back to cited text no. 6
    

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Correspondence Address:
Amanjit Bal
Department of Histopathology, Postgraduate Institute of Medical Education and Research, Sector 12, Chandigarh - 160 012
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0377-4929.200037

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