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Garneau M, Alyzadneh E, Lal G, Rajan Kd A. Metastatic Disease to a Concurrent Thyroid Neoplasm: A Case Series and Review of the Literature. Head Neck Pathol 2023; 17:447-459. [PMID: 36719557 PMCID: PMC10293528 DOI: 10.1007/s12105-022-01509-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Accepted: 11/12/2022] [Indexed: 02/01/2023]
Abstract
BACKGROUND Metastatic disease to the thyroid gland is uncommon but well-described. Metastatic disease to a concurrent primary thyroid neoplasm is a rare phenomenon. We sought to study patients with metastasis to the thyroid with a focus on the histopathologic and clinical features in tumor-to-tumor metastasis. METHODS We identified a series of patients with metastatic disease to the thyroid, with or without a concurrent primary neoplasm, through a search of the files of the Department of Pathology. All relevant slides were retrieved and reviewed, including routine HE and immunohistochemical stains. We performed a detailed English language literature search (1962-2022) and review to identify tumor-to-tumor metastasis involving the thyroid. RESULTS We identified 14 patients with metastasis to the thyroid over a 22-year period. Four patients exhibited papillary thyroid carcinoma, with metastatic spread of a different malignancy seeding into the thyroid cancer. We describe the histopathologic diagnostic process and findings, clinical management, and the clinical course of tumor-to-tumor metastasis in greater detail for these 4 patients. CONCLUSION Tumor-to-tumor metastasis to the thyroid is a rare event with unique histopathologic features. Our findings suggest that the phenomenon of tumor-to-tumor metastasis serves to highlight broader mechanisms of metastatic disease in general. We provide the largest-to-date and comprehensive review of the literature to identify all previous reported instances of tumor-to-tumor metastasis involving the thyroid.
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Affiliation(s)
- Michael Garneau
- University of Iowa Roy J. and Lucille A. Carver College of Medicine, 52242, Iowa City, IA, USA
| | - Eyas Alyzadneh
- Department of Pathology, University of Iowa Hospitals and Clinics, Iowa City, IA, 52242, USA
| | - Geeta Lal
- Department of Surgery, University of Iowa Hospitals and Clinics, 52242, IA, Iowa City, USA
| | - Anand Rajan Kd
- Department of Pathology, University of Iowa Hospitals and Clinics, Iowa City, IA, 52242, USA.
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Abdullah AM, Qaradakhy AJ, Ahmed MM, Salih AM, Omar SS, Kakamad FH, Rahim HM, Abdulla BA, Mohammed SH, Ahmed SF, Baba HO, Ishaac RH. Thyroid collision tumors; A case series with literature review. Ann Med Surg (Lond) 2022; 76:103444. [PMID: 35299940 PMCID: PMC8921309 DOI: 10.1016/j.amsu.2022.103444] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 02/19/2022] [Accepted: 02/27/2022] [Indexed: 12/24/2022] Open
Abstract
Background Collision tumors are two histologically distinct types of malignancies within the same mass and organ. The aim of this study is to present a case series of thyroid collisions. Methods This was a multicenter retrospective case series study. The participants were consecutive in order. Socio-demographic and clinical data were obtained from hospital records. Results The study included eight cases comprising six (75%) females and two (25%) males. The patients had different presentations, including neck swelling, dyspnea, and dizziness. The pathology was successfully determined through fine-needle aspiration. Four patients (50%) underwent lobectomy, whereas the other half (four patients) underwent total thyroidectomy. Conclusion Collision tumors of papillary thyroid cancer (PTC) and follicular thyroid carcinoma (FTA) or medullary thyroid carcinoma (MTC) and FTA are exceedingly rare phenomena that most commonly affect females. Complete or partial thyroidectomy is the ideal management of choice for these cases and is associated with good survival. Collision tumors are two distinct types of malignancies with dissimilar cellular lineages and genetic origins within the same mass. Patients with thyroid collision tumors have rarely been observed in the literature. Most thyroid collision tumors consisting of papillary and medullary carcinoma. In this study, several cases of thyroid collision tumors have been discussed.
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Clinicopathological and Molecular Features of Secondary Cancer (Metastasis) to the Thyroid and Advances in Management. Int J Mol Sci 2022; 23:ijms23063242. [PMID: 35328664 PMCID: PMC8955551 DOI: 10.3390/ijms23063242] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2022] [Revised: 03/10/2022] [Accepted: 03/14/2022] [Indexed: 12/19/2022] Open
Abstract
Secondary tumours to the thyroid gland are uncommon and often incidentally discovered on imaging. Symptomatic patients often present with a neck mass. Collision tumours of secondary tumours and primary thyroid neoplasms do occur. Ultrasound-guided fine-needle aspiration, core-needle biopsy, and surgical resection with histological and immunohistochemical analysis are employed to confirm diagnosis as well as for applying molecular studies to identify candidates for targeted therapy. Biopsy at the metastatic site can identify mutations (such as EGFR, K-Ras, VHL) and translocations (such as EML4-ALK fusion) important in planning target therapies. Patients with advanced-stage primary cancers, widespread dissemination, or unknown primary origin often have a poor prognosis. Those with isolated metastasis to the thyroid have better survival outcomes and are more likely to undergo thyroid resection. Systemic therapies, such as chemotherapy and hormonal therapy, are often used as adjuvant treatment post-operatively or in patients with disseminated disease. New targeted therapies, such as tyrosine kinase inhibitors and immune checkpoint inhibitors, have shown success in reported cases. A tailored treatment plan based on primary tumour features, overall cancer burden, and co-morbidities is imperative. To conclude, secondary cancer to the thyroid is uncommon, and awareness of the updates on diagnosis and management is needed.
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Sugianto I, Yanagi Y, Hisatomi M, Okada S, Takeshita Y, Bamgbose B, Asaumi J. Collision tumor of small cell carcinoma and squamous cell carcinoma of the maxillary sinus: Case report. Mol Clin Oncol 2022; 16:96. [PMID: 35400122 PMCID: PMC8985071 DOI: 10.3892/mco.2022.2529] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Accepted: 01/27/2022] [Indexed: 11/22/2022] Open
Abstract
A collision tumor refers to the coexistence of two diagnostically distinct tumors in a common anatomic space. Collision tumors are rare in the oral and maxillofacial region. The present study reported on the case of an 82-year-old female with a collision tumor in the maxillary sinus consisting of small cell carcinoma (SmCC) and squamous cell carcinoma (SCC). Computed tomography (CT) imaging revealed a mass in the right maxillary sinus. The lesion exhibited heterogeneous low signal intensity (SI) on T1-weighted imaging (T1WI), high SI on short T1 inversion recovery and heterogeneous solid enhancement on contrast-enhanced T1WI. The histopathology result of a biopsy specimen confirmed SmCC. After the patient received a course of chemoradiotherapy, follow-up CT revealed a residual tumor. In a second surgery, a remaining tumor and histopathology revealed SCC with no evidence of SmCC. The final diagnosis was a collision tumor made up of SCC and SmCC.
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Affiliation(s)
- Irfan Sugianto
- Department of Oral Radiology Faculty of Dentistry Hasanuddin University, Makassar, Sulawesi 90245, Indonesia
| | - Yoshinobu Yanagi
- Department of Dental Informatics, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Science, Okayama 700‑8558, Japan
| | - Miki Hisatomi
- Department of Oral Diagnosis and Dentomaxillofacial Radiology, Okayama University Hospital, Okayama 700‑8558, Japan
| | - Shunsuke Okada
- Department of Oral Diagnosis and Dentomaxillofacial Radiology, Okayama University Hospital, Okayama 700‑8558, Japan
| | - Yohei Takeshita
- Department of Oral and Maxillofacial Radiology Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Science, Okayama 700‑8558, Japan
| | - Babatunde Bamgbose
- Department of Oral and Maxillofacial Radiology Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Science, Okayama 700‑8558, Japan
| | - Junichi Asaumi
- Department of Oral Diagnosis and Dentomaxillofacial Radiology, Okayama University Hospital, Okayama 700‑8558, Japan
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Bojoga A, Stănescu L, Badiu C. Collision tumors of the thyroid. A special clinical and pathological entity. Arch Clin Cases 2022; 8:84-90. [PMID: 34984231 PMCID: PMC8717004 DOI: 10.22551/2021.33.0804.10191] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Thyroid collision tumors are rare entities that designate two histologically and morphologically distinct tumors that occur simultaneously or as metastases from other organs within the thyroid. Medullary and papillary carcinoma co-occurrence is the most frequent. Several theories tried to explain the pathogenic mechanisms underlining collision tumors, including the theory which assumes that one tumor predisposes the other, stem cell theory, and random effect theory, but their combination better explains the origin of these tumors. Hypotheses about common genetic behavior responsible for the pathogenesis have also been suggested, such as the involvement of germline mutation of RET (Rearranged during Transfection) proto-oncogene in medullary thyroid carcinoma and papillary thyroid carcinoma coexistence, but there is controversy on this topic. Management of thyroid collision tumors is challenging owing to the presence of two distinct tumors with different biological aggressiveness, treatments options, and prognosis, and needs to be individualized.
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Affiliation(s)
- Andreea Bojoga
- "Carol Davila" University of Medicine and Pharmacy, Bucharest, Romania; "C.I. Parhon" National Institute of Endocrinology, Bucharest, Romania
| | - Laura Stănescu
- "Carol Davila" University of Medicine and Pharmacy, Bucharest, Romania; "C.I. Parhon" National Institute of Endocrinology, Bucharest, Romania
| | - Corin Badiu
- "Carol Davila" University of Medicine and Pharmacy, Bucharest, Romania; "C.I. Parhon" National Institute of Endocrinology, Bucharest, Romania
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Straker RJ, Modi MB, Elder DE, LiVolsi VA, Fraker DL, Xu X, Karakousis GC. A case of tumor-to-tumor metastasis of cutaneous malignant melanoma. J Cutan Pathol 2020; 47:1196-1199. [PMID: 32740977 DOI: 10.1111/cup.13829] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 07/27/2020] [Accepted: 07/28/2020] [Indexed: 11/27/2022]
Abstract
We report a case of tumor-to-tumor metastasis of a cutaneous malignant melanoma to a synchronous thyroid Hurthle cell carcinoma. A 42-year-old male underwent a biopsy of right inguinal lymphadenopathy which showed metastatic melanoma. The primary lesion was identified on his right posterior leg, and staging workup discovered a synchronous left thyroid lobe nodule concerning for a follicular neoplasm. He underwent excision of the primary melanoma, right inguinal lymphadenectomy, and total thyroidectomy. The resected thyroid contained a 6.6-cm, well-encapsulated left-sided nodule, red-brown in color and homogenous in consistency, with areas of focal hemorrhage and no grossly identifiable calcification. Microscopically, large tumor cells with distinct cell borders were present, with deeply eosinophilic and granular cytoplasm, large nuclei with prominent nucleoli, and loss of polarity consistent with oncocytes. A microscopic single focus of vascular invasion was identified, and a diagnosis of angioinvasive Hurthle cell carcinoma was made. Within the Hurthle cell carcinoma, multiple deposits of metastatic melanoma were seen. These findings were indicative of tumor-to-tumor metastasis of the cutaneous melanoma to the angioinvasive Hurthle cell carcinoma. Our findings show the ability of melanoma to metastasize to a pre-existing neoplasm.
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Affiliation(s)
- Richard J Straker
- Department of Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Mitul B Modi
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - David E Elder
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Virginia A LiVolsi
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Douglas L Fraker
- Department of Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Xiaowei Xu
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Giorgos C Karakousis
- Department of Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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Khalil J, Elomrani F, Benoulaid M, Elkacemi H, Kebdani T, Errihani H, Benjaafar N. Isolated thyroid metastasis revealed an unknown lung adenocarcinoma: a case report. J Med Case Rep 2015; 9:221. [PMID: 26410084 PMCID: PMC4584122 DOI: 10.1186/s13256-015-0663-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 07/28/2015] [Indexed: 12/26/2022] Open
Abstract
INTRODUCTION Cancer metastasis to the thyroid is extremely rare. The most common sites that have been reported to metastasize to the thyroid gland are breast and kidney. As to primary lung cancer metastasizing to the thyroid gland, only a few cases have been described in the literature. CASE PRESENTATION We report a case of a 37-year-old white Arabian woman who had never smoked tobacco products for whom a malignant thyroid mass revealed a primary lung tumor. She had a surgical excision for both the thyroid and the pulmonary tumors, and received adjuvant chemotherapy. At 1 year, she is still in remission. CONCLUSIONS Our case is rare as it describes a case where the thyroid lesion was the revealing sign of an unknown lung carcinoma. Management of thyroid metastases should depend on the individual situation and surgical excision should be proposed whenever a patient's condition is favorable.
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Affiliation(s)
- J Khalil
- Radiation oncology department, National Institute of oncology, Mohamed V University, Rabat, Morocco.
| | - F Elomrani
- Medical oncology department, Mohamed V University, Rabat, Morocco.
| | - M Benoulaid
- Radiation oncology department, National Institute of oncology, Mohamed V University, Rabat, Morocco.
| | - H Elkacemi
- Radiation oncology department, National Institute of oncology, Mohamed V University, Rabat, Morocco
| | - T Kebdani
- Radiation oncology department, National Institute of oncology, Mohamed V University, Rabat, Morocco
| | - H Errihani
- Medical oncology department, Mohamed V University, Rabat, Morocco
| | - N Benjaafar
- Radiation oncology department, National Institute of oncology, Mohamed V University, Rabat, Morocco
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Ryan N, Walkden G, Lazic D, Tierney P. Collision tumors of the thyroid: A case report and review of the literature. Head Neck 2015; 37:E125-9. [PMID: 25491252 DOI: 10.1002/hed.23936] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/05/2014] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Collision tumors of the thyroid are a rare pathology that present a diagnostic and treatment challenge. In this report, we present an interesting case and a review of the current literature as to inform management. METHODS AND RESULTS An 88-year-old woman presented with acute airway compromise and vocal cord paralysis. CT identified a thyroid mass and widespread metastasis. Histopathology identified the lesion as a collision tumor consisting of a squamous cell carcinoma (SCC) and papillary thyroid carcinoma. The patient was managed with surgery and palliative radiotherapy. However, she died from complications of a lower respiratory tract infection. We also present a review of the literature with 33 cases reviewed. CONCLUSION Management of collision tumors is complex because of the duality of the pathology. They should be managed in a multidisciplinary team setting and treatment should be patient specific. Generally, the most aggressive neoplasm should guide treatment. We recommend surgical management with adjunct therapy.
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Affiliation(s)
- Neil Ryan
- United Bristol Healthcare NHS Trust, ENT Bristol, United Kingdom
| | - Graham Walkden
- North Bristol NHS Trust, Surgery Bristol, United Kingdom
| | - Darko Lazic
- Great Western Hospital, Histopathology Swindon, United Kingdom
| | - Paul Tierney
- United Bristol Healthcare NHS Trust, ENT Bristol, United Kingdom
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Sathiyamoorthy S, Maleki Z. Cytomorphologic overlap of differentiated thyroid carcinoma and lung adenocarcinoma and diagnostic value of TTF-1 and TGB on cytologic material. Diagn Cytopathol 2013; 42:5-10. [PMID: 23637102 DOI: 10.1002/dc.22997] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 11/29/2012] [Accepted: 03/19/2013] [Indexed: 11/10/2022]
Abstract
Thyroid carcinomas and lung adenocarcinoma share cytomorphological features yet have different prognoses. Thyroid Transcription Factor-1 (TTF-1) is an immunohistochemical (IHC) marker used to confirm pulmonary and thyroid carcinoma, while Thyroglobulin (TGB) is expressed by thyroid carcinoma. The cytopathology archive of The Johns Hopkins Hospital was searched for cases of lung adenocarcinoma versus thyroid carcinoma with TTF-1 and TGB IHC. Forty-four cases of lung adenocarcinoma (25) and thyroid carcinoma (19) were retrieved. One was metastatic lung adenocarcinoma to the thyroid and three were metastatic papillary thyroid carcinoma (PTC) to the lung. The initial interpretation of two cases from bony lesions was metastatic lung adenocarcinoma. In light of additional clinical information and TGB immunostain, the diagnoses of these two cases changed to metastatic thyroid carcinoma. TTF-1 and TGB is a small immunostain panel that can differentiate lung adenocarcinoma from thyroid carcinoma and prevent misdiagnosis and its consequences.
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Affiliation(s)
- Srividya Sathiyamoorthy
- Department of Pathology, Division of Cytopathology, The Johns Hopkins Hospital, Baltimore, Maryland
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10
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Stevens TM, Richards AT, Bewtra C, Sharma P. Tumors metastatic to thyroid neoplasms: a case report and review of the literature. PATHOLOGY RESEARCH INTERNATIONAL 2011; 2011:238693. [PMID: 21559195 PMCID: PMC3090057 DOI: 10.4061/2011/238693] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/28/2010] [Accepted: 01/31/2011] [Indexed: 11/20/2022]
Abstract
Metastasis into a thyroid neoplasm-tumor-to-tumor metastasis-is exceedingly rare. We describe the 28th documented case of a tumor metastatic to a thyroid neoplasm and review the literature on tumor-to-tumor metastasis involving a thyroid neoplasm as recipient. All cases showed a recipient thyroid neoplasm with an abrupt transition to a morphologically distinct neoplasm. Metastasis into primary thyroid neoplasm was synchronous in 33% of cases and metachronous in 67%. Follicular adenoma was the most common recipient thyroid neoplasm overall (16/28), and papillary thyroid carcinoma was the most common malignant recipient neoplasm (9/28). Of the 9 recipient papillary carcinomas, 6 were follicular variants. Renal cell carcinoma was the most common neoplasm to metastasize to a primary thyroid neoplasm (9/28), followed by lung (6/28), breast (5/28), and colon (3/28) carcinoma. Tumor-to-tumor metastasis should be considered whenever a dimorphic pattern is encountered in a thyroid tumor.
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Affiliation(s)
- Todd M Stevens
- Department of Pathology, Creighton University Medical Center, Omaha, NE 68131, USA
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Moalem J, Choi DX, Khanafshar E, Ruan DT, Woeber KA, Clark OH, Kebebew E. Metastatic papillary thyroid cancer misdiagnosed as non-small [corrected] cell lung cancer. Thyroid 2011; 21:319-23. [PMID: 21254936 DOI: 10.1089/thy.2010.0395] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
BACKGROUND Thyroid and lung cancers, two malignancies with similar immunohistological characteristics, have vastly different biologic behaviors and treatment approaches. As thyroid cancers commonly spread to the lungs, metastatic thyroid cancer should be included in the differential diagnosis of a pulmonary lesion or lesions. SUMMARY A 54-year-old woman with a remote history of stage IV nonsmall cell lung cancer was found to have FDG avidity in the thyroid and right cervical lymph nodes. Subsequent ultrasonographic findings and FNA cytology led to a total thyroidectomy, bilateral central lymphadenectomy, and right modified radical lymph node dissection for primary thyroid cancer. Reviews and comparisons of the pulmonary and cervical surgical specimens revealed that the patient had been misdiagnosed for the previous 6 years; she had metastatic papillary thyroid cancer to the lung. The patient's original diagnosis of stage IV lung cancer was based upon the original lung biopsy showing positive thyroid transcription factor-1 (TTF-1) immunostaining. The original diagnosis was questioned because of her long survival when she was diagnosed with locally advanced papillary thyroid cancer. Further analyses of the immunohistological characteristics of both surgical specimens--including staining for TTF-1, thyroglobulin, CD57, S-100, and CEA--documented the correct diagnosis. CONCLUSIONS A thorough understanding of the natural history and surgical pathology, including immunohistology, of lung and thyroid cancers is necessary for a correct and timely diagnosis and appropriate treatment. Because TTF-1 expression is seen in both thyroid and lung cancers, careful consideration should be given to both malignancies when evaluating patients with thyroid and pulmonary nodules.
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Affiliation(s)
- Jacob Moalem
- Division of Surgical Oncology, Department of Surgery, University of Rochester, Rochester, New York 14642, USA.
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Dias AR, Pinto RA, Mory E, Silva IC, Siqueira SAC, Nahas SC, Cecconello I, Wexner SD. Synchronous collision malignant melanoma and adenocarcinoma of the rectum. Tech Coloproctol 2010; 14:181-4. [PMID: 20309715 DOI: 10.1007/s10151-010-0571-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2009] [Accepted: 06/22/2009] [Indexed: 02/07/2023]
Abstract
"Collision tumors" consist of two independent but coexisting tumors. This uncommon situation might be easily mistaken for a composite tumor where one histogenetic event originates from two apparently distinct neoplasms. Colorectal collisions are particularly unusual; here, we report the exceedingly rare case of a 61-year-old man with malignant melanoma and adenocarcinoma colliding in the rectum. Collision tumors have an idiopathic pathophysiology and in fact "accidental meeting" is accepted by many authors. This article discusses the concepts about cancer development, which are overlooked by this hypothesis, another theory to explain that this rare occurrence involves microenvironment changes.
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Affiliation(s)
- A R Dias
- Department of Gastroenterology, Hospital das Clinicas, University of Sao Paulo, Sao Paulo, Brazil
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