Small cell carcinoma
history,| , Image = Small cell lung cancer - cytology.jpg | , Caption = Micrograph of a small cell carcinoma of the lung showing cells with nuclear moulding, minimal amount of cytoplasm and stippled chromatin. FNA specimen. Field stain. | , OMIM = | , OMIM_mult = | , MedlinePlus = 000122 | , eMedicineSubj = med | , eMedicineTopic = 1336 | , DiseasesDB = | , MeshID = D018288 | }} Small cell carcinoma is a type of highly malignant carcinoma usually associated with the lung, though it can be associated with other topographies, such as in cervical cancer or prostate cancer.
Types
Paraneoplastic Syndromes: Small cell carcinomas produce ACTH and ADH, which can lead to SIADH.
Lung
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When associated with the lung, it is sometimes called "oat cell carcinoma" due to the flat cell shape and scanty cytoplasm.
It is thought to originate from neuroendocrine cells (APUD cells) in the bronchus called Feyrter cells (named for Friedrich Feyrter).
Hence, they express a variety of neuroendocrine markers, and may lead to ectopic production of hormones like ADH and ACTH that may result in paraneoplastic syndromes.
It is more metastatic than non-small cell lung carcinoma (and hence staged differently) and is sometimes seen in combination with squamous cell carcinomas. There is usually early involvement of the hilar and mediastinal lymph nodes.
Chapter 13, box on morphology of small-cell lung carcinoma in: 8th edition.
Smoking is a significant etiological factor.
Symptoms and signs are as for other lung cancers. In addition, because of their neuroendocrine cell origin, small cell carcinomas will often secrete substances that result in paraneoplastic syndromes such as Lambert-Eaton myasthenic syndrome.
On histopathology, small-cell lung carcinoma generally appears as a pale gray mass located centrally (near the hilum). It generally extends into the lung parenchyma. It is composed of tumor cells with a round to fusiform shape, scant cytoplasm, and finely granular chromatin. Mitoses are frequently seen. Cell necrosis is always present and may be extensive. The tumor cells often show cell fragmentation. There is also nuclear molding (the shape of one nucleus conforms around the shape of an adjacent nucleus»The Ohio State University College of Veterinary Medicine > VM 618 cource > Glossary of Terms Retrieved on Feb 12, 2010) resulting from tumor cells with scant cytoplasm lying close to each other.
It can metastasize to the brain.
Prostate
In the prostate, small cell carcinoma is a rare form of cancer. Due to the fact that there is little variation in prostate specific antigen levels, this form of cancer is normally diagnosed at an advanced stage.
Treatment for small cell lung carcinoma
Typically, treatment for small cell lung carcinoma is dependent on what stage the cancer is at. In cases of limited-stage small cell lung carcinoma,combination chemotherapy, often consisting of a cyclophosphamide, cisplatinum, doxorubicin, etoposide,vincristine and/or paclitaxel. Thoracic irradiation may or may not improve survival in limited stage small cell lung carcinoma. In this setting, initial response rates are exceptionally high with chemotherapy alone, but relapse is quite common, though up to 40-50% of patients with limited stage disease may survive two years,according to one study. Overall, between 60-90% of patients with limited stage small cell lung carcinoma respond to chemotherapy, and 45-75% of patients have a complete response, but median survival is only 18-24 months. As small cell lung carcinoma spreads rapidly and is highly responsive to chemotherapy, there is little role for surgery in the treatment of limited stage small cell lung carcinoma, however,some have hypothesized that in cases of asymptomatic, node negative small cell lung cancer, surgical excision may improve survival when used prior to chemotherapy. In extensive disease, combination chemotherapy is the standard of care, with radiotherapy added only to palliate symptoms such as dyspnea, pain from liver or bone metastases, or for the treatment of brain metastases, which, in small cell lung carcinoma,typically have a rapid, if temporary, response to whole brain radiotherapy. Combination chemotherapy consists of a wide variety of agents,including cisplatin, cyclophosphamide, vincristine and carboplatin. Response rates are high even in extensive disease, with up 15-30% of patients with extensive stage small cell lung carcinoma having a complete response to combination chemotherapy and the vast majority of patients having at least some response to combination chemotherapy. However,responses are often of short duration. If in either limited or extensive disease, complete response to chemotherapy occurs, then prophylatic cranial irradiation will often be considered to prevent brain metastases. Although this treatment is likely effective to prevent brain metastases from small cell lung carcinoma, it can cause cognitive changes, hair loss, headache and radiation necrosis of the brain and it is unclear weather it provides any survival benefit. All in all small cell carcinoma is very responsive to chemotherapy and radiotherapy in particular the platinum based agents. However, most people with the disease relapse and median survival remains low in both limited and extensive stage disease.
Prognosis
In limited stage disease, median survival with treatment is 14-20 months, and about 20% of patients with limited stage small cell lung carcinoma live 5 years or longer. The prognosis is far worse in extensive stage small cell lung carcinoma, with treatment, median survival is just 8-13 months, and only 1-5% of patients with extensive stage small cell lung carcinoma treated with chemotherapy live 5 years or longer.
References
Additional images